(58 U-S. NATIONAL MUSEUM BULLETIN 260 



cephalic lobes, shortness of article 5 of antenna 2, shape of epistome, 

 conditions of gnathopods, coxa 6, pleonal epimera and pleonite 4. 

 Orchomene tabasco differs from all five members of the complex in the 

 shorter cleft of the telson (40% as compared to 50 + % ) and the absence 

 of eyes. It further differs from O. mlnuta in the slight expansion of 

 coxa 1, from O. lepidula in coxa 1 and the shorter inner ramus of uro- 

 pod 3, from 0. intermedia in the smaller posterior lobe of coxa 5, from 

 most forais of 0. pinguis in the broader lobe on article 5 of gnathopod 

 1 but differs in no other gross characters from O. minuscula than those 

 mentioned above for all five species. 



Stivipatric relationships. — Orchomene tabasco resembles Orcho- 

 mene holmesi (Hurley, 1963) especially in its gnathopods, pleonal 

 epimera and pereopods, but differs by the protrusion of the epistome 

 anterior to the upper lip, the narrower cephalic lobes, the presence of a 

 posteroventral lobe on coxa 6, the shape of article 2 on pereopod 5 and 

 the longer fifth article of gnathopod 1. Orchomene anaquela J. L. 

 Barnard (1964a) bears eyes, a poorly produced coxa 6 and a narrower 

 article 2 of pereopod 5. The fourth coxa of the juvenile of 0. tabasco 

 is like that of O. anaquela^ the posteroventral lobe being more quadrate 

 than in the adult of O. tabasco. Orchomene anaquela occurs on the 

 Californian coastal shelf in a depth of 33 meters. 



There is a strong resemblance of O. tabasco to Uristes dawsoni 

 Hurley (1963). Although U. daiosoni is justifiably placed in Uristes 

 because of its small head, the slight anteroventral bevelment of coxa 

 1 and the position of the mandibular palp, U. dawsoni might better be 

 placed in the genus Orchomene. Species of Uristes generally have 

 the posteroventral corner of coxa 1 beveled, the mandibular molar setu- 

 lose and the mandibular palp occurring directly opposite the molar. 

 Even if the type-species, U. gig as (Dana) {siVict.= Try phosa antenni- 

 potens Stebbing, 1888), has a poorly beveled posteroventral corner of 

 coxa 1, the other characters are congruent. Indeed, U. dawsoni is an 

 intergrade between Uristes and Orchomene. The resemblance of O. 

 tabasco to U. dawsoni occurs in the prebuccal complex and pleonal epi- 

 mera ; the head of U. dawsoni is only slightly narrower than it is in O. 

 tabasco, the mandibular j)alp is only slightly more proximally located, 

 the fifth article of gnathopod 1 is scarcely shorter, the hand of gnatho- 

 pod 2 is only slightly stouter and less strongly chelate, article 2 of 

 pereopod 5 is only slightly less broad and more synunetrically ex- 

 panded, the accessory flagellum is somewhat shorter, and the spines 

 on the medial edge of the outer plate of the maxilliped are more 

 distinct. 



