NO. 1659. AMERICAN SPECIES OF SYNALl'IIEUS—COVTIERE. 1>J 



group is at present much less restricted than that of the Brevicarpus 

 group, since it is known in the Indian Ocean, on the west coast of 

 Africa, and in the jVIediterranean. If the idea of time couhl be intro- 

 duced into these data, one woukl say that the diti'erentiation of the 

 Brevicarpits group is more recent; thus would also be exi:)lained 

 its presence exclusively in America as well as its coexistence with 

 the Paulsoni group, from which it has come, and its relatively small 

 number of species. All these characters are opposed to the much 

 wider distribution of the L.evimanus group, to the localization of 

 the derived species of the Biunguiculatus group and to the exces- 

 sive development of the forms which characterize the L^vimanus 

 group. 



The armature of bristles of the small claw gives to these forms a 

 connnon aspect so characteristic that it can hardly be believed, in a 

 superficial examination, that there is room for so great a number of 

 species within a compass of differences apparently so slight. It is, 

 however, probably true even further than I have indicated, that 

 several of the races or subsj^ecies have a specific value. On the whole, 

 one may say that the species of this group tend toward the elongation 

 of the wrist of the small claw and the suppression of the antennal 

 scale. These two tendencies are met with occasionally within the 

 same form, such as S. longica7'jnis, in which the length of the wrist 

 varies from once to twice the width wdth the age of the specimens. 

 But there are grafted onto this general plan some characters quite 

 unexpected, such as the curious form of the fingers of the small claw 

 in S. pectiniger, the excavated meropodites of S. androsi, and the 

 basicerite with a longitudinally .spinous superior surface, of S. rath- 

 huiue. No other group gives the impression as does this one of hav- 

 ing sprung from a single species, by " explosion " of its characters 

 (to employ the expression of Standfuss), characters which might be 

 regrouped by chance like a combination of letters. 



Remarkable from a morphological point of view, the L^vimanus 

 group is no less remarkable as to conditions of existence. It is the 

 only one in which a single haul of the dredge of the U. S. Fish- 

 eries steamer Albatross (Station 2413) has been able to bring up 

 from 5,000 to 3,000 .specimens (belonging to the two species, S. longi- 

 carpus (Herrick) and /S. pectinigtT Coutiere). It is this group in 

 W'hich anomalies in the laying of eggs are met with most frequently ; 

 among 227 females of S. pectiniger (Station 2413), of which I have 

 determined the sex by examining them singly with the greatest care, 

 I have been able to find only two or three in which the pleura were 

 normal and the eggs pre.sent, and have been able to find none Avith the 

 very large eggs carried by the normal females. The males which 

 accompany them are 320 in number, with some closely united, all 

 inferior in size to the normal. I propose to conduct investigations 

 Proc. N. M. vol. xxxvi— 09 2 



