346 GEOLOGICAL SURVEY OF THE TERRITORIES. 



2-jomted, 2d joiut about two-tbirds longer than the 1st, taperi^j? towards 

 the end; basal joint curved a little at the base. 2d antenna? or clasp- 

 ers large and tortuous ; the basal joint extends outward and downward ; 

 the 2d joint extends backward parallel to the body, and is bent atriglit 

 angles to itself, and the 2a is directed forwards and inwards, the ends 

 nearly meeting over the median line of the body; 3d joint siiort, swol- 

 len, and subdividing into three branches, the longest of which reaches 

 in its natural position to the 8th segment behind the 1st anteunary seg- 

 ment. Au antenniform appendage springs from the end of the basal 

 joint and reaches to the end of the 5th ring behind the eyes; it is slen- 

 der, flattened, and much as described in S. similis Baird. At the end 

 on the outside of the 2.1 joint is an acute, short, flat, conical a[»pendage. 

 Of the two terminal large appendages, the longer and slenderer one is 

 sinuate and sends ofl:* a slender spur from the base, reaching nearly to 

 the bend in the appendage, where there is a slight projection, beyond 

 which it is long and slender, flattened, cylindrical. The other append- 

 age is irregularly flattened, very sinuate, and about two-thirds as long- 

 as the other. Near the base on the outer edge are two flat lamellate 

 teeth, the inner much the smaller and slenderer; the outer broad and 

 suddenly ending in a finger-like point, the appendage ending abruptly 

 in an acute point. For want of material it is difficult to draw up a good 

 comparative description of the appendages of this species as compared 

 with A. floridanus and A. sealii. 



By reference to the figures on Plate XII a good idea of the form of 

 the appendages and their endites and exites can be obtained; but which 

 characters are generic and which specific would be difficult to say. The 

 Istendite is broad and large, with long, fine, hair-like setae; in the 8th 

 pair the base of the ed'ge of the 5th endite has six stout, truncated, short 

 spines (see PI. XII, fig. 5 ^=). The gills are oval, lanceolate in form; 

 the flabellum rather broad and well rounded on the outer edge, which 

 is serrate, the teeth giving rise to small, tine setaB. 



The male reproductive organs arise from the 8th segment counting 

 forward from the telsoii, or the 15th from the head, and are slender, 

 simple, unarmed, cylindrical, of the same thickness throughout, with 

 the end blunt, and are curved around so as to touch at their origin. 



Telson very short; caudal appendages but slightly separated at base, 

 long and rather stout, gradually tapering to the end and well fringed 

 on both edges. 



Length of the whole animal, IG.2'"'^; length of longer appendage of 

 2d antennae, 4.2™'"; length of caudal stylets, 3.2-""'; length of penis, 

 3.2-'". 



Female. — Differs from the male in the 2d antenna?, which scarcely reach 

 beyond the 1st antennae, and which are flat, conical, ending in a finger- 

 shaped point. Ovisac attached to the 13th and 14th segments behind 

 the head ; it reaches backwards to the segment in front of the telson, 

 forming a long cylindrical sac ending in two valves, the upper one tri- 

 angular, hollowed beneath, the under one short, forming the end of the 

 ovisac. The external opening of the oviducts are situated on the basal 

 segment of the abdomen. The eggs are a little the larger at the end of 

 the ovisac. The caudal appendages are rather shorter and considerably 

 stouter than in the male. 



Total length, 14'"'"; of caudal appendages, 3'""'; of ovisac, 5"^"". 



This description is mainly based on the few examples received from 

 Waco, Tex., through Mr. G. W. Belfrage, who found it in 1871, and again 

 February 17, 1872,\vith Limnetis and Estheria. Afterwards a large num- 

 ber, mostly immature, were received from Dr. Watson, at Ellis, Kaus., and 



