ON THE SYNCARIDA. 125 



fifth joint thicker thiiii tiie foiutli, thiclveninj;' towards the di.stal end, with four spines, the fonrth 

 spine tbc largest and as long as the joint is tiiick ; the sixth about two-thirds as thick as the fifth, 

 with two remote spines on the under side and ending in two spines, one of them very large and 

 stout (there is possibly a third snuill spine). In Meek and Worthen's figures the s[)in('S are errone- 

 ously drawn on the outer side of four joints; we find that the spines ate situated only on the two 

 penultimate joints; the terminal claw is not represented by Meek and Worthen. The succeeding 

 six pairs are all about the same size and length, being large, well developed, long, and slender, 

 about one half to two-thirds as thick as the first pair (406''), with no traces of a gill ; the second 

 pair are a little stouter than the others and apparently spiued on the penultimate joint ; the sev- 

 enth pair the slenderest and nearly as long as the first pair; the three basal joints are long and 

 slender, the third very distinct, long, and slender; fourth joint long, slightly swollen in the mid- 

 dle; fifth equal to the sixth in length, but slender, slightly thickened towards the distal end; the 

 sixth somewhat longer than the fifth, ending in a point ; none of the terminal joints appear to be 

 chelate. 



The abdominal appendages are distinctly biramous and schizopodal iu their api)earance. Each 

 apparently consists of a small, narrow, jointed limb and a larger exopodital branch (or gill(?) ; see 

 406-'''''). We can see traces of the first two pairs. In another specimen (aOL^'^) the first three pairs 

 of abdominal legs are to be plainly seen; the exopodital or respiratory and swimming ramus is 

 sessile, lanceolate-oval, and broad, thickened on the hinder (?) edge. In Mr. Garr's specimen No. 

 1 are distinct traces of a biramous appendage on the fourteenth and fifteenth (penultimate) seg- 

 ments ; and in his No. 3 there are to be seen the traces of the second-fourth pairs of abdominal feet, 

 with double rami, the hinder ramus the smaller and narrower. In an abdominal foot (in Lacoe's 

 No. 406PS) the second joint is narrow, lanceolate-oval, rounded at the tip, from which arise a series 

 of long slender setie, about twelve in number, which form an oar-like appendage equaling in size 

 the basal joint; total length of the limb 14.5""" (the basal joint 8""", the row of setae 6.5"" ^14.5™'"). 

 These legs remind us somewhat of those of Squilla, as do the first thoracic pair, from their being 

 larger than the others and armed on the under side with stout spines. 



The telsou is very long and slender, narrow, acute, the end very slender, with long set£e on 

 each end ; it is a little longer than the caudal feet (uropoda) on each side of it. The caudal feet, 

 or sixth pair of uropoda, are divided into two long, large, acute rami (endopodite and exopodite) 

 arising from a small, short basal joint (Garr's No. 1). The two rami are of nearly the same size 

 and length, both edges of each branch being setose (the setae are not so numerous and close as 

 represented in Meek and Worthen's figure). 



Of forty specimens examined, the total length of the largest example, including the caudal 

 appendages, but not including the antennae, was 75°"" (Lacoe's No. SS"""); another still larger 

 (No. X*) ^3s 85""" in length; a specimen received from Mr. Garr was 58"™ in length. 



In a specimen of A. eveni, 45""' iu length, 1 made the following measurements: Width of 

 the body, b-T"""' (in Lacoe's 501'' : Width of first cephalic segment, 5.5"""; of second segment, 6™""; 

 length of first and second head-segments together, G"™ ; length of rostrum, l™""; length of sixth seg- 

 ment, 3.5""") ; length of first anteuna3, about 12"""; length of second antennae, 20'"™; length of first pair 

 of feet, 20'"'"; greatest width of filth joint of first feet, 2'""-; length of abdominal feet, 18-19"'"'; length 

 of telson, 13"""; length of caudal appendages, fi™™. 



Many of the specimens are preserved flattened out, showing the back, with the legs spread 

 out symmetrically on each side; others are preserved lying on their side, with the body somewhat 

 arched, and then they present a shrimp-like appearance, though on a superficial examination 

 reminding one of an Amphipod lying on its side. 



The foregoing remarks apply to the larger specimens described by Meek and Worthen as 

 Acanthotehon eveni. I cannot with certainty point out any distinctions from A. stimpsoni M. & W., 

 the first-described species; the smaller specimens, which might be referred to the latter species, 

 are evidently the young of A. eveni M. and W. Hence the specific name should be Stimpsoni. 



The characters of this Crustacean are such as to forbid our referring it to any known group; 

 we therefore suggest that it forms the type of a suborder of thoracostracous Crustacea, which we 

 would designate as the Syncarida. 



What we should regard as the diflereutial characters of the group Syncarida, to which Acautho- 



