DECAPOD CRUSTACEANS OP THE BEAUFORT, N. C, REGION. 443 



Genus PINNOTHERES Latreille. 



Pinnotheres Latreille, 1802. p. 25. 



KBY TO THE SPECIES OF THE BEAUFORT REGION. 



a. Carapace nearly naked; second pair of legs stouter than third pair ostreum. 



aa. Carapace covered with a short pubescence; secondpairof legs not stouter than third pair, .maculatus. 



Pinnotheres ostreum Say. Oyster crab. PI. xxxv, fig 9. 



Pinnotheres ostreum Say, :8i7, p. 67: De Kay, 1843, p. 12; Stimpson, 1859, p. 67; Smith, 1873, p. 367; R- Rathbun, 18S4. 

 p. 76s; Paulmier, 1903, p. 149; Sumner, 1911, p. 674; Fowler, 1912, p. 138. 



Carapace of female subcircular in outline, tumid, membranous, smooth, and with a broad, shallow, 

 longitudinal depression at each side of the cardiac and gastric areas; front roimded, slightly produced, 

 covering and concealing the eyes. Abdomen very large and broad, extending forward to the mouth 

 parts and laterally to or beyond the bases of the legs. 



Eyes, antennules, and antennae greatly reduced. Chelipeds small, the articles subcylindrical and 

 polished; hand weak, its superior margin elevated above base of movable finger; fingers short, the 

 immovable one conical and pubescent on its inner surface, movable one slenderer and curved. Second 

 pair of legs slender but stouter than the others and with the penultimate article swollen; third pair 

 longest, fifth pair turned backward and upward. 



Measurements of a female: Length of carapace, 9mm.; width, 11 mm.; length of hand, 4.5 mm. 



Color: Female, in life, whitish or salmon pink. 



This well-known commensal of the oyster has been collected in various parts of the Beaufort region, 

 and doubtless is distributed generally throughout the area. It is females alone, however, which are 

 abundant; no specimen of the male has yet been obtained at Beaufort. In the National Museum, 

 among more than a hundred females, collected at many localities and at various seasons, Dr. Mary J. 

 Rathbtm has found but a single very small and immature male. By S. I. Smith the male of P. ostreum 

 is said to be free swimming. The scarcity of the sex in collections indicates that this may be true, 

 but it is also possible that Smith mistook the unspotted form of the next species for the male of P. 

 ostreum. 



Pinnotheres maculatus Say. Pinna crab, mussel crab. PI. xxxv, fig. 10. 



Pinnotheres maculatum Say, 1818, p. 450. 



Pinnotheres maculaius Siijnpsou, 1859, p. 67; Coues,i87i, p. 123; Kingsley, 1878-79, p. 323; R. Rathbun, 1884, p. 766; Sum- 

 ner, 1911, p. 674; Fowler, 1912, p. 136-137. 

 Pinnotheres ostreum Smith, 1873, pi. 1, fig. 2. 



Carapace of female semimembranous, suborbicular, somewhat narrowing anteriorly, the sides being 

 obliquely truncated; median regions defined by deep, irregular sulci; surface covered with a dense 

 but very short pubescence; front bilobate. Abdomen very large, as in P. ostreum. 



Cheliped moderately stout, its articles subcylindrical and more or less pubescent; hand well devel- 

 oped, its palmar portion about twice as long as the fingers, both of which are nearly straight, hooked at 

 their tips and toothed. Walking legs slender, with short ctirved dactyli, none of them conspicuously 

 larger than the others, the penultimate article of the second pair not swollen; last pair smallest and 

 turned forward and upward and with longer dactyli than those of the other legs. 



The males differ from the females in being much smaller, firmer in texture, and flatter; the cheli- 

 peds are shorter and stouter and the second and third pairs of walking legs have the carpal and propodial 

 articles densely fringed with silky hairs. 



Measurements of a female: Length of carapace, 16 mm.; width, 17.25 mm.; length of hand, 9 mm. 



Measturements of a male: Length of carapace, 8.4 mm.; width, 7 mm.; length of hand, 3.5 mm. 



In this crab there are two distinct color phases — one is a plain, almost uniform yellowish-brown, 

 the other has the carapace black or dark brown with a central dorsal stripe and two symmetrical spots 

 of white, while the sternum and abdomen are white with narrow bars of black. Heretofore the uni- 

 formly colored individuals have been regarded as females and the spotted ones as males, but a recent 

 examination by Dr. Mary J. Rathbim, of the specimens in the National Museum, shows that this is 

 not always the case. The males, both yoiuig and adult, are usually spotted, but are sometimes plain. 

 The females are usually spotted when yoting, but are always plain colored when adult. 



