Chasmocarcinus cylindricus Rathbun, 1901 (Figs. 3 C‒E; 21F; 28G; 35K, L; 49F; 56E; 64A‒F; 84D; 89D) Chasmocarcinus typicus Rathbun, 1898a: 285 [Trinidad] (part). Not Chasmocarcinus typicus Rathbun, 1898. Chasmocarcinus cylindricus Rathbun, 1901: 10, fig. 1 [type localilty: Puerto Rico]; 1918: 55 [in key], 59, figs. 28, 29.— Serène 1964a: 258 [in list].— Soto 1985: 483, 487 [Straits of Florida].— Blow & Bailey 1992: 176 [in list].— Melo 1996: 419 [in key], 420 [unnumb. fig. not C. cylindricus] [Brazil]; 1998: 494 [in list].—Coelho & Coelho 1998: 813 [in list].—Ng et al. 2008: 76 [in list].—Felder et al. 2009: 1081 [in list]. ? Chasmocarcinus aff. cylindricus — Guinot et al. 2013: 279 [“South America”]. Type material. Neotype: female (4.6 × 6.1 mm) (USNM 23765), Puerto Rico, Mayagüez Harbor, U.S. Fish Commission Porto Rico Expedition, 1898‒99, Fish Hawk, stn 6061, 22‒ 33 m. Other material examined. Puerto Rico. Neotype female (4.6 × 6.1 mm), 2 males (4.0 × 5.2 mm, 3.5 × 4.0 mm), 1 female (5.4 × 6.9 mm) (USNM 23765), 2 males, 2 females (USNM 24552), Mayagüez Harbor, U.S. Fish Commission Porto Rico Expedition, 1898‒99, Fish Hawk, stn 6061, 22‒ 33 m, stn 135(6063), 137–139 m; 1 female (6.9 × 9.2 mm) (USNM 24551), stn 181(6059), 13 m; 1 male (cw 6.2 mm) (USNM 24550), off Aguadilla, stn 167 (6055), 251 m.— 1 male, 1 female (USNM 67774), Johnson-Smithsonian Expedition; 1 male, 2 females (USNM 67775), stn 10, 18°30’24”N, 66°04’15”W, 201 m; 5 males, 5 females (USNM 67773), stn 36, 18°30’30”N, 66°23’5”W, stn 730, 18°31’30”N, 66°18’20”W, 1 female (4.0 × 4.9 mm) (USNM 67798), stn 104, 18°30’10”N, 66°13’50”W, 91 m, 08.03.1933.—1 male, 1 female (USNM 99359), La Parguera, J.A. Rivero coll., 15 m, 0 2.1955. Guadeloupe. KARUBENTHOS 2012: 2 males (MNHN-IU-2013-9002), 3 males, 4 females (MNHN-IU-2013- 9003) [photographed], Anse à la Barque, stn GD12, 16°05.52’N, 61°46.59’W, 45 m, 09.05.2012; 1 male, 1 female (MNHN-IU-2013-9001) [photographed], Anse à la Barque, stn GD15, 16°05.39’N, 61°41.48’W, 50 m, 10.05.2012; 1 male (MNHN-IU-2013-9000), Îlot Cochon, stn GD46, 16°13.02’N, 61°32.89’W, 10 m, 20.05.2012; 15 males, 19 females (MNHN-IU-2013-13077); 1 female (MNHN-IU-2013-8998), stn GD47, 16°12.95’N, 61°33.03’W, 13 m, 20.05.2012; 10 juveniles (MNHN-IU-2013-8999), stn GD48, 16°11.21’N, 61°32.51’W, 27 m, 20.05.2012; 79 males, 93 females, 1 juvenile (MNHN-IU-2013-13078); 7 male, 9 females (MNHN-IU-2013-13076), stn GD56, 16°18.73’N, 61°32.29’W, 18 m, 20.05.2012. Barbados. 1 male (2.3 × 2.8 mm) (USNM 110239), 91–366 m, J.B. Lewis coll. Trinidad. 1 juvenile female [part of type material of C. typicus Rathbun, 1898] (USNM 6901). — 2 males, 1 female (USNM 139265), Gulf of Paria, 9 m, J.M. Stanley coll., 19.01.1971. Jamaica. 1 male (3.6 × 4.9 mm) (USNM 42942), Montego Bay. Panama. CARIB 1: 1 male (3.0 × 3.7 mm) (USNM 1277739), 08°54.7’N, 77°41.0’W, Alpha Helix, 30 m, 29.06.1977. Colombia. 1 male, 1 female (USNM 107149), Ceycen I., 29 m, R. Lemaitre et al. coll., 0 6.08.1995. Diagnosis. Carapace (Fig. 3 C‒E) proportionally wide along anterior third; conspicuous ridge of sharp granules around post-ocular, anterolateral margins of carapace. Orbits (Fig. 21 F) long, eye peduncles short. Epistome (Fig. 21 F, 64E, F) with semicircular median lobe with median fissure, lateral margins straight. Antennular articles relatively short (Fig. 21 F). Third maxilliped (Fig. 28 G) ischium quadrate, about same length as merus. Bulging pterygostomial region, clearly visible from dorsal view. Fingers of major chela of large males (Fig. 35 K) proportionally short, only slightly longer than propodus in dorsal view; pollex as long as dactylus in large males (Rathbun 1918: fig. 29a). Fingers of minor chela of both sexes (Fig. 35 L) scissor-like; with small, sharp teeth. Inner margin of cheliped carpus smooth. Ambulatory legs (Fig. 3 C‒E) proportionally long, folded P5 merus almost reaching anterior margin; subdistal spur present on P5 dactylus. Fused thoracic sternites 1, 2 (Fig. 49 F) broadly triangular, proportionally wide, short. Male pleon (Figs. 49 F, 56E) with proportionally long, narrow telson (Rathbun 1918: fig. 29b). G1 (Fig. 64 A‒C) stout, distal part thickened, distal segment straight with spinules. G2 (Fig. 64 D) about 3/4 G1 length, straight, slender, distal segment long, curved. Female pleon (Fig. 84 D) with lateral margins of somites strongly convex; telson proportionally short. Sterno-pleonal cavity of female (Fig. 89 D) moderately shallow, vulvae close together. Remarks. Characteristic of the species is its carapace (Figs. 3 C‒E), which is proportionally wide along its anterior portion, giving it a quadrate appearance; the presence of a conspicuous ridge of sharp granules around the post-ocular and anterolateral margins of the carapace; and the proportionally long orbits and short eye peduncles (Fig. 21 F). Also diagnostic are the third maxillipeds, which have a quadrate ischium that is about the same length as the merus. The lot that included the holotype (USNM 2365) originally contained four males and two females and a note by M.J. Rathbun (“largest ♂ is holotype ”) but it currently contains only two males and two females with a note (“ holotype ♂ prepared by SEM by W. Blow”). The holotype could not be found so it is presumed lost (K. Reed, personal communication). The two extant males are unfortunately incomplete, each lacking the pleons and the second specimen the two gonopods. A complete female from the same lot (4.6 × 6.1 mm, USNM 2365) is therefore selected as the neotype of Chasmocarcinus cylindricus Rathbun, 1901. A female from Puerto Rico (6.9 × 9.2 mm, USNM 24551) is considerably larger than the rest of the material examined. Its epistome shows some differences, with a more salient median lobe (semicircular in small individuals) and lateral lobes with slightly more elevated lower margins than in small individuals, differences that are perhaps a consequence of size. The specimen was erroneously illustrated by Rathbun (1918: fig. 28) as showing short orbits instead of the diagnostic long orbits, which were observed, together with the diagnostic ridge along the post-ocular and anterolateral margins of the carapace, in the actual specimen. Distribution. Florida, West Indies, Panama and Colombia to Brazil (south to São Paulo state). Depth: 9–1967 m (Felder et al. 2009).

Published as part of Ng, Peter K. L. & Castro, Peter, 2016, Revision of the family Chasmocarcinidae Serène, 1964 (Crustacea, Brachyura, Goneplacoidea), pp. 1-182 in Zootaxa 4209 (1) on pages 18-20, DOI: 10.11646/zootaxa.4209.1.1, http://zenodo.org/record/272646