90 U.S. NATIONAL MUSEUM BULLETIN 260 



tionable in light of the conditions in various European species of 

 Tmetonyx. The type-species, Tmetonyx cicada (Fabricius) has a 

 rectangular first coxa whereas other species have the tapered first 

 coxa of '"'•Tryphosa^'' with Tmetonyx acutus (Sars, 1895) representing 

 the fully reduced tryphosa condition. Tmetonyxes also, regardless of 

 coxae, bear large teeth on the first gnathopodal dactyls, in contrast to 

 the ordinary species of ^''Tryfliosa^''; some species of ^'' Tryphosa^'' 

 however, have been described bearing these teeth so that definitely 

 congeneric species have been assigned to different genera. Perhaps 

 Tmetonyx should be retained for its type-species having the dactylar 

 tooth and normally rectangular coxa and the other tmetonyxes as- 

 signed as a subgeneric group to '"''Tryphosa^'' (see Tryphosella above). 

 This viewpoint is discussed in other places in this paper in relation 

 to other problems. 



If first coxae were disregarded as generic criteria some species of 

 Hipponiedon, Anonyx, TrypJwsites, '"''Tryplwsa^'' and Uristes might 

 fall into the same genus. Nevertheless, the various tmetonyxes dem- 

 onstrate the difficulty in defining Uristes and '"'' Tryphosa''' just on their 

 type-species or typical species. The heads of various species of 

 Tmetonyx are intermediate in size between those of Uristes and ''''Try- 

 pliosa'"' and the mouthpart projections vary from the weak condition 

 of Tmetonyx acutus to the strong condition of Tmetonyx similis Sars. 

 Another method of treating this problem would be the amalgamation 

 of Uristes, ''''Tryphosa,^'' and Tmetonyx (and other genera already 

 synonymized with Uristes by J. L. Barnard, 1962a), or the retention 

 and creation of various subgeneric names to segregate facies such as 

 the Tmetonyx group with normal first coxae, the '"''Trypliosa^'' group 

 with modified first coxae, the group of tmetonyxes with dactylar teeth 

 and tryphosal first coxae {Uristoides Schellenberg, 1931, is an avail- 

 able appellation), and the Uristes group with small head and small 

 prebuccal clusters. This procedure should not be attempted until the 

 prebuccal complex of the type-species of Uristes can be studied more 

 thoroughly. Ambasiopsis might form the fifth member of the group 

 and a sixth group might be comprised of Uristes lepidus and 

 U. perspinis. 



The amalgamated tryphosa complex differs from the genera Anonyx 

 Kr0yer and Trypliosites Sars by the distally uncxpanded (and often 

 tapering) first coxa. As a parallel revision Trypliosites Sars might 

 be assig-ned to Anonyx as a subgenus. 



The generic value of first gnathopods is not altogether lost in the 

 amalgamation of Uristes, '"'"Tryphosa^'' and their allies because most 

 species of Uristes have an elongated sixth article and most species of 

 '•'■Trypliosa^'' have an elongated fifth article. 



