279 



channels to the branchial cavity, near the base of the chelipeds; some of the anastomosing 

 lines of the carapace extend also to the subhepatic and pterygostomian regions. Buccal cavity 

 quadrate, with the lateral borders subparallel and the anterior angles rounded. External 

 maxillipeds parallel, rather broad, leaving only a narrow gap between than (fig. 3«); 

 upper margin of ischium and merus neither grooved nor hairy ; ischium longer than broad 

 and distinctly longer than merus, suture between them very distinct, merus broadly-oval, 

 nearly circular, external margin rather regularly curved ; palp inserted at its summit '), longer 

 than merus, consisting of three joints, placed end to end, dactylus somewhat longer than 

 propodus; exognath thick, but flattened at outer surface, for the greater part exposed, almost 

 half as broad as the ischium and not narrowing towards its summit. 



The chelipeds and some of the walking legs are lost; on the left side the ambulatory 

 legs of the second, third and fourth pair, on the right only those of the fourth pair are extant. 

 These remaining legs regularly decrease in length from before backward, the longest leg measuring 

 exactly the breadth of the carapace. Some darker spots and bands are observed on their surface, 

 in conformity with the pattern on the carapace. Mero-, carpo- and propodite are entirely smooth 

 and hairless ; the dactyli are provided with a few short hairs, about half as long as preceding 

 propodites and made up of two parts, resembling those of the Xanthidae : the basal and 

 greater portion is conical, thick and entirely straight, sharply marked off from the slender, 

 horny, curved tip. 



The abdomen of the 9 is large, elongate (fig. 3<^), covering the whole sternum and 

 with a ribbon-like elevation in the middle, thickly fringed along the margins, the sutures 

 separating the joints are wavy, and the last segment is the longest, nearly semi-circular. There 

 are no eggs in my specimen. 



The only known specimen has been collected long ago (in 1864) by Hoedt at Amboyna. 



Dimensions in mm. : 



Fronto-orbital distance 11. — 



Length of carapace 20.5 



Breadth of carapace 24.— 



Length of second pair of walking legs . 24. — 



Length of fourth pair of walking legs . 21. — 



Opisthopus Rathbun. 

 1893. Opisthopus Rathbun. Proc. U.S. Nat. Mus., v. 16, p. 251. 



This genus was referred to the Asthetiognathinae by the author herself, on account of 

 the ischium of the external maxillipeds being distinctly developed (probably longer than the 

 merus); there is, however, some resemblance to the Pimiotherhiae, and especially to the genus 

 Scleroplax, by the dactylus of these maxillipeds being inserted at the inner border of the pro- 

 podus. It is to be regretted that this essential feature has never been figured. Alcock ranged 

 the o-enus for some unknown reason among the Pinnotherelinae. Only one species is known. 



l) , Affixed to its internal angle'' according to DE Man. 



131 



