MUSEUM OF COMPARATIVE ZOOLOGY. 15 



vas deferens) of the last thoracic somite of the male, which arises from the 

 right coxa, and is curved in one plane round the right side of the abdomen ; 

 while in Spiropagurus the appendage arises from the left coxa, and is spirally 

 curved. 



The carapax is short and broad, and the anterior margin is obtuse, and does 

 not wholly cover the ophthalmic somite between the eyes. The portion in 

 front of the cervical suture is indurated, but all the rest of the carapax is very 

 soft and membranaceous, without any distinct induration along the cardiaco- 

 branchial suture. The ophthalmic scales are well developed. The eye-stalks 

 are short and the cornea expanded. The antennulse, antennae, and oral ap- 

 pendages are similar to those in Ewpagurus ; the exopods of all the maxillipeds 

 are, however, proportionally much longer than in that genus. There are 

 eleven pairs of phyllobranchise, arranged as in Ewpagurus bemhardus, but the 

 two anterior pairs connected with the external maxillipeds are very small, and 

 composed of a few flattened papilla?. The chelipeds are slender and unequal. 

 The first and second pairs of ambulatory legs are long, and have slender, com- 

 pressed, and ciliated or setigerous dactyli ; the third pair are only imperfectly 

 subcheliform. 



In the male, the second, third, and fourth somites of the abdomen bear small 

 appendages upon the left side, as in most of the allied genera, but the fifth 

 somite is destitute of an appendage ; in the female, the appendages of the 

 second, third, and fourth somites are biramous and ovigerous, and there is 

 usually a rudimentary uniramous appendage upon the fifth somite, as in the 

 allied genera.* The uropods are very nearly or quite symmetrical, the rami 

 of the right appendage being very nearly or quite as large as that of the left. 

 The telson is bilobed at the extremity. 



As might be expected, the unsymmetrical development of the external sexual 

 appendages of the males of the two species here described corresponds to a like 

 unsymmetrical development of the internal sexual organs, and the following 

 incomplete observations, made on ordinary alcoholic specimens in which the 

 abdominal viscera are not sufficiently well preserved for a full anatomical or 

 histological investigation, appear of sufficient importance to notice here, espe- 

 cially as nothing appears to be known of the internal structure of either species 

 of Spiropagurus. 



The right testis and vas deferens are much larger than the left. The lower 

 part of the right vas deferens, in all the adults examined, is much more dilated 

 than the left, and is filled (as is also the external part of the duct) with very 

 large spermatophores of peculiar form. The left vas deferens is slender, much 

 as in Eupagurus bemhardus, terminates in a small opening in the left coxa of 

 the last thoracic somite, as in ordinary Paguroids, and contains spermatophores 

 somewhat similar in form and size to those of Eupagurus bemhardus. In alco- 



* In many of the best preserved and most perfect females of C. socialis examined 

 I can find no trace whatever of this appendage of the fifth somite, while in others it 

 is very easily seen. 



