NO. 1659. AMERICAN SPECIEti OF SlYNALPIIEUS—COUTIERE. ]5 



The Brevicarpus ^roup is extremely like the Paulsoni group, 

 and it is very possible that it may have been derived from the latter; 

 the absence of an inferior vertical prolongation of the rostrum, the 

 fact that all the species known have the carpocerite elongated, often 

 swollen, indicate derivative and not primitive forms. On the other 

 hand, it is there that are found the species having the largest antennal 

 scale {S. brevicarpus Herrick), which is a character directly opposed 

 to the preceding; but S. brevicarpus is a species with very large eggs 

 producing mysis, a character which appears especially to show 

 itself in- those forms which are most highly developed. Finally, 

 the Brevicarpus group is, up to the present time, exclusively Ameri- 

 can. Should its presence be established in some part of the Indo- 

 Pacific — in Australia, for instance — the American region would 

 surely remain its true country. Compared to the preceding groups 

 it has an unusual distribution, inasmuch as the species which com- 

 pose it extend from the Bermudas to Brazil and from California to 

 Ecuador, exactly like the American forms of the Paulsoni or 

 Neomeris groups. These last appear to have had rather an Indo- 

 Pacific origin, if one may judge by the number and variety of the 

 forms which represent them in that region. One is led then to 

 wonder if the origin of the Brevicarpus group ought not to be 

 sought for also in some of the species of the Paulsoni groups; this 

 might have found only in American waters the conditions which 

 have brought about its variations in the direction of the Brevicarpus 

 group. 



Being given the form brevicarpus, the most typical species with 

 small eggs is S. minus (Say), from which one is able to derive an 

 " oxyceros " form from Brazil, an antiUensis form with antennules 

 short and carpocerite more swollen, and a form with antennules very 

 long and slender, S. digneti Coutiere from Lower California. A form 

 of this species, S. ecuadorensis, exists upon the Pacific coast of South 

 America. The species S. brevicarpus (Herrick) with very large eggs 

 differs in its more slender carpocerite and larger antennal scale. It 

 is the largest species of Si/nalpheus known. All these species are 

 separated by slight differences. It is probable that /S. minus (Say) 

 comprises several " races " other than those indicated here and be- 

 haves as does 8. paulsoni in the Indo-Pacific region. 



The Biunguiculatus group includes among its species S. nep- 

 tunus (Dana), the types of which I have been able to examine, and 

 specimens of which have also been sent me from Australia by Mr. 

 McCulloch. S. laticeps Coutiere, of the Maldives, is very like it. 

 These two species have the finger of the small chela widened and 

 spatuliform, ornamented besides with some long hairs, which in S. 

 neptunus are arranged in rows. These hairs are directed obliquely 

 downward, and isolated, which is not the usual disposition in the 



