PYCNOGONIDS 



265 



especially broad in the female, where it may equal the width of the pro- 

 boscis ; at the dorsodistal border is a long conical protuberance armed 

 with a strong spine which usually projects distally; /.i and t.2 equal, 

 stout ; all these joints armed more or less densely with moderate spines, 

 which are longer, however, on the dorsal side of /.i and 1.2. First tarsal 

 joint small, subtriangular, with short, even spines; ts.2 moderately 

 strong, arcuate, armed dorsally and on the sides with rows of slender 

 spines, and ventrally with 3 strong spines at the heel and a row of 

 very short ones along the sole; cl. about one half ts.2.\ aux. cl. well 

 developed, half as long as cl. In the male the genital projection on the 

 ventrodistal side of c.2 of the 2 posterior pairs of legs is pronounced 

 and thumb-like, and provided with i or 2 slender bristles. As is charac- 

 teristic of the genus, the genital openings of the female are in a corre- 

 sponding position on all 4 pairs of legs, but are not situated on similar 

 protuberances. 



Length about 4 mm., extent 16 mm.; the two sexes nearly the same 

 size. 



Immature specimens. Four immature specimens of this species were 

 examined, two from each locality where the form was taken. They are 

 but little smaller than the adults, which they closely resemble, but are 

 provided with chelate chelifori (pi. xvn, fig. i), and the ovigera are very 

 short, with indistinct articulations (fig. 2). It is interesting to note that 

 the denticulate spines are already forming in this early stage, in a space 

 beneath the outer cuticle (fig. 3), and at the next moult would probably 

 be free. If any of these specimens were males there was no trace at this 

 stage of the genital protuberances ; in fact, the genital openings were not 

 distinguishable at all. 



SPECIMENS EXAMINED. 



Remarks. Whereas Ammothea alaskensis may be taken as the repre- 

 sentative of A. lavis (Hodge) in the Western Hemisphere, A. latifrons 

 more closely approaches those forms grouped about the European species 

 A. echinata (Hodge). It may readily be distinguished from any described 

 species, however, by its very broadly elliptical proboscis and the long, 

 knobby chelifori and caudal segment. This species is about twice the 

 size of A. echinata. 



