166 U.S. NATIONAL MUSEUM BULLETIN 2 60 



L-shaped, scarcely convex posteriorly, coxa 4 smaller than coxa 3, 

 obreniform; pereopods 1 and 2 with sixth articles equal to (pereopod 

 1) or longer than (pereopod 2) fifth articles, sixth articles distally ex- 

 panded, anterodistal ends each having one large seta, posterodistal 

 ends each bearing two conspicuous locking-spines, dactyls short and 

 clawlike but not as modified as those of P. bouvieri, each dactyl (and 

 those of pereopods 3-5) with large, partially fused inner seta and one 

 minute lateral submarginal setule; pereopods 3 and 4 with sixth articles 

 as long as or longer than fifth, expanded second articles with sub- 

 quadrate posteroventral corners and nearly straight posterior margins ; 

 pereopod 5 longer than 4, with strongly expanded, dorsoventrally nar- 

 row but anteroposteriorly elongated and rounded lobe, articles 5 and 

 6 subequal to each other and scarcely shorter than article 4 (badly 

 damaged and not illustrated) ; pleonites 1-3 posterodorsally serrate, 

 consecutively with about 6, 5, and 3 serrations, pleonites 4 and 5 each 

 with small posteromedial tooth; pleonal epimera all intersimilar, 

 posterior margins convex, posteroventrally sinuous, each with small 

 posteroventral tooth ; uropods 1-3 in poor condition, similar to those of 

 P. louvleri as figured by J. L. Barnard (1964b) but each ramus with 

 at least 1 long, distally articulated spine and apparently no marginal 

 spines (unless broken off, sockets not apparent) ; uropod 3 with asym- 

 metrically and bilaterally cuspidate ramal apices, each bearing one 

 spine of medium length, one small seta and one very large socket of 

 missing spine presumably much longer than remaining spine ; telson 

 typical, elongated, cleft to base, each lobular apex with one medium 

 spine and one setule. 



HoLOTYPE.— AHF No. 6038, male, 3.0 mm. 



TYPE-LOCALrrY.— Station 7230, 27°52'25" N, 115°44'30'' W, 2667- 

 2706 m, Dec. 31, 1D60. 



Material. — Two specimens from the type-locality. 



RFJ.ATIONSHIP.— This species bridges the distinctions between the 

 genera Tbwi Liljeborg and Pseudotiron Chevreux. It combines the 

 gnathopods of Pseudotiron with coxa 3 of Tiron; however, the gnatho- 

 podal distinctions of the species at hand are only of quantitative degree 

 in comparison with 7'iron. They involve the elongated article 6 and 

 the basally unexpanded article 5. The head of P. coas resembles that 

 of various species of Pseudotiron more than that of various species of 

 Tiron. This resemblance includes the extensive anterolateral cephalic 

 excavation at the insertion point of antenna 1, resulting in a strangely 

 dorsal position of the antennal base and a broad, flat anterocephalic 

 margin, which projects and partially locks the first article of antenna 

 1 in the groove between the lateral margin and the weak anteromedial 

 cephalic ridge. The elongation of the peduncular articles of antenna 



