NO. 1659. AMERICAN SPECIES OF SYNALPHEUS—COUTIERE. 



83 



In the second pair the fli'st segment of the carpus, the sum of the 

 four following, and the di.stal chela are apparently of the same length. 



The third pair is very characteristic of the species. Like the small 

 chela of jS. pectinlgci\ its form is, so far as known, unicjue in the genus 

 Synalpheus. Its proportions are: Meropodite 1.75; carpus 1; propo- 

 dite 0.92. The meropodite is 3 times as long as wide; its ventral bor- 

 der is widened in the distal half into a flattened surface, which is a 

 little excavated, and margined on the outer side by a transparent 

 wing, on the inner side by a crest much less visible, but bearing some 

 short, strong hairs. 



The very elongate carpus, also flattened on the ventral side, is like- 

 w^ise bordered by an outer wing larger than that of the meropodite 

 and capable of concealing it. On the inner side, the crest w^hich bor- 

 ders it bears 5 teeth and some hairs. The propodite itself has upon 

 nearly all its length a crest which seems to be determined by the 

 pressure of that article against the lower border of the meropodite 



Fig. 50. — Synalpheus andeosi. a, frontal and antennal region ; K, large chela ; 

 k, small cheliped of first pair ; m, foot of third pair ; m', dactyl of third pair; 

 m", CARPUS and meropodite of third pair ; t, telson. 



w^hen the leg is fully bent. In this position — which explains why the 

 form of the carpus is more curved than is customary near its articu- 

 lation — the distal end of this article is applied against a short non- 

 excavate portion of the flattened meral surface, so that between it 

 and the surface of the carpus there exists an interval closed outwardly 

 by the two transparent superimposed plates. There exists in some 

 species of Alp hens of the " erinifvs ""' group, such as A. paraleyone^ a 

 form somewhat analogous but much less accentuated. The two hooks 

 of the dactyl are almost equal and a little divergent. 



The telson bears on its posterior border 11 plumose hairs between 

 the inner spines, which are 3 times as long as the outer spines. The 

 external ramus of the uropod bears a small movable spine between two 

 adjacent teeth. 



The type is a female from Andros Island, Bahamas; F. Stearns 

 collection (Cat. No. 38409, U.S.N.M.). 



