50 U.S. NATIONAL MUSEUM BULLETIN 2 60 



armed distally with one pair of simple spines; coxa 4 with quadrate 

 posterodistal lobe, corners blunt; pereopods 3-5 remarkably similar 

 among themselves, posteroventral corners of lobes on second articles 

 rounded, stenopodous articles (3-7) successively more slender, fourth 

 articles poorly expanded and weakly produced distoventrally ; postero- 

 ventral corner of first pleonal epimeron rounded but bearing micro- 

 scopic tooth, corners of epimera 2 and 3 sharply quadrate, bearing 

 microscopic teeth, posterior margins nearly straight ; pleonite 4 dor- 

 sally straight from lateral view, slightly elevated above following 

 pleonite ; uropods 1 and 2 bearing lateral peduncular spines, one spine 

 on outer rami, two on inner, mner ramus of uropod 2 not incised; 

 inner ramus of uropod 3 scarcely exceeding article 1 of outer ramus; 

 telson longer than broad, cleft two thirds of its length. 



HoLOTYPE. — AHF No. 6131, male, 2.6 mm. Unique. 



Type-locality.— Station 7249, 27°36'25" N, 115°56'25" W, 3705- 

 3745 m, Jan. 4, 1961. 



Relationship. — The generic assigmnent of this species is uncertain. 

 Coxa 1, uropod 2, and the mandibular molar resemble those of ^''Try- 

 phosa''' but the maxillary spines are as stout as those of Schisturella 

 and Pseudoneshnus (both genera are considered synonymous herein). 

 Coxa 1 and the mandibular molar, however, are more specialized than 

 in typical tryphosas; the first coxa is slightly smaller than that of 

 '•'•TryplioscC'' and resembles that of Schisturella grabenis, new species; 

 the mandibular molar is smaller than that of typical '"''TryphoscC (and 

 JJristes) , and has very few setules and a few faint ridges and cusps. 

 The intermediacy of these characters suggests a Imk between tryphosas 

 and schisturellas. This link would contradict a presumption that 

 schisturellas have been derived from hippomedon-like ancestors 

 through reduction of first coxae, because it indicates that tryphosas 

 with first coxae already reduced but with setulose molars may have 

 been modified through reduction of setules. On the other hand, schis- 

 turellas may be polyphyletic and have originated from both tryphosas 

 and hippomedons. A7nbasio2?sis fomes difi'ers from all species of 

 /Schisturella by the simple imier ramus of uropod 2. 



The new species is assigned provisionally to Ambasiopsis K. H. 

 Barnard (see 1932) because of the partially setulose mandibular 

 molar, the general reduction (but not overall shape) of coxa 1 and the 

 shape of the upper lip and epistome. Ambasiopsis differs from ''^Try- 

 phosa'"' especially in the prebuccal complex, which in Tryphosa has a 

 lobate epistome dominating the upper lip, whereas the reverse is true 

 of Ambasiopsis. Ainbasiopsis fomes differs from the type-species 

 of Ambasio2)sis by the presence of spines on the outer plate of the 

 maxilliped, the tryphosa-like shape of the reduced first coxa and espe- 



