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 
aleoholic specimens in which the abdominal viscera are not sufliciently 
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 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 Lupagurus bernhardus, 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 Hupagurus bernhardus. In alcoholic specimens of H. 
socialis the spermatophores from the left vas deferens are approximately 
0.16™™ long 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" long and a third as broad ; 
at one end it terminates in a very 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 0.35°" 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, and are apparently of 
about the same size. 
Hemipagurus 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 antennie, the middle lobe thus 
formed being scarcely more prominent than the lateral lobes, each of 
*In many of the best preserved and most perfect females of Hemipagurus socialis 
examined I ean find no trace whatever of this appendage of the fifth somite, while in 
others it is very easily seen. 
