PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 423 



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 ex- 

 tremity. 



As might be expected, the unsymmetrical development of the external 

 sexual appendages of the males of the two species here described cor- 

 responds 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, especially as nothing appears to 

 be known of the internal structure of either species of Spiroparjurus. 



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 i^art of 

 the duct) with very large spermatophores of peculiar form. The left vas 

 deferens is slender, much as in EupagurKS bcrnhardus, 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 hernliardm. In alcoholic specimens of H. 

 sociaUs the spermatophores from the left vas deferens are approximately 

 QKjmm iQjjg and 0.035'"™ broad, with a slender neck about a third of the 

 entire length, and a very thin and delicate lamella for a base. The 

 spermatophores from the right vas deferens are over 2°"" in total length ; 

 the body itself is oval, approximately 0.40™™ looig and a third as broad; 

 at one end it terminates in a vevy long and slender process, two or three 

 times as long as the body ; at the other end there is a similar but slightly 

 stouter process, a little longer than the body, and expanding at its tip 

 into a broad and very delicate lamella, approximately O.oo™'" long by 

 0.20'"'" broad. The contents of the two kinds of spermatophores are, of 

 course, not in a condition to show the structure of the spermatozoa, but 

 they present a similar appearance in each case, aud are apparently of 

 about the same size. 



Hem'lpagurus socialis, sp. nov. 



Male. — The part of the carapax in front of the cervical suture is about 

 a fifth broader than long; the sides nearly parallel ; the front margin 

 sinuous, curving slightly forward in the middle and each side between 

 the eye-stalks and the peduncles of the antennaj, the middle lobe thus 

 formed being scarcely more i^romineut than the lateral lobes, each of 



* In many of the best preserved and most perfect females of Hemipaf/nrus socialis 

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

 others it is very easily seen. 



