164 U.S. NATIONAL MUSEUM BULLETIN 2 60 



Relationship. — This species resembles B. diodon K. H. Barnard 

 (1916, and see J. L. Barnard, 1962a) but the dorsal teeth of B. diodon 

 occur on pereonite 7 and pleonite 1 and no tooth occurs on pleonite 4. 



Young individuals of this species, less than 2.0 mm long, lack the 

 dorsal teeth of pereonite 7 and pleonites 1 and 2 but have the tooth of 

 pleonite 4 fully developed. Most specimens 4.0 mm long or longer 

 (to 5.5 mm) have all of the dorsal teeth fully developed but a few 

 specimens exceeding 4.0 mm lack the tooth of pereonite 7. Fifteen 

 of the 29 specimens from 7229 have all teeth fully developed and all 

 are 4.0 mm or longer but 14 specimens, most of which are shorter than 

 4.0 mm, lack either the tooth of pereonite 7 or all of the teeth. 



Distribution. — Middle Baja California, 1748-2398 m. 



Pseiidotiron Chevreux 



Pseudotiron (?) coas, new species 



, Figure 81 



Description. — Head not strongly extended anterodorsally, rostrum 

 terminating bluntly on anterior portion of head, separated from an- 

 terior cephalic keel by deep incision, anterolateral cephalic margin 

 nearly vertical, straight, anteroventral corner rounded subquadrately ; 

 eyes absent ; first antennal peduncle elongated, article 3 slightly longer 

 than article 2, accessory flagellum 2-articulate; antennal flagella having 

 elongated articles ; basal article of first antennal flagellum not bearing 

 typical sensory setae of male Pseudotiron; antenna 2 with elongated 

 flagellar articles and a minute sixth ; mouthparts similar to those of 

 P. longicaudatus Pirlot (1934) but mandibular palp stouter, article 

 3 with two setae, article 2 lacking setae, mandibular body with only 

 three or four setae in setal row; lower lip illustrated herein; maxilla 1 

 with four setae on medial lobe, seven spines on lateral lobe; medial 

 lobe of maxilla 2 not as broad as in P. longicaudatus ; outer maxilli- 

 pedal plate with only three large distal spines, none on medial margin, 

 two of spines characteristically ridged (see figure) ; gnathopods of 

 typical pseudotiron morphology but stouter than in type-species, P. 

 houvieri Chevreux, fifth articles not expanded proximally as in genus 

 Tiron Liljeborg ; coxa three nearly perfectly rectangular, not typically 



Figure 81. — Pseudotiron (?) coas, new species, holotype, male, 3.0 mm, 7230: a,h, 

 head, with and without antenna 1; c, half of telson; d, apex of inner ramus of uropod 2; 

 ej, gnathopods 1,2; g, peduncular article 3 and flagella of antenna 1; h, peduncular article 

 5 and flagellum of antenna 2; t, two apical spines of outer plate of maxilliped; ;, maxilli- 

 pedal inner and outer plates; k-o, pereopods 1,2,3,4,5; p, uropod 3, with spine missing on 

 each ramus; q, lower lip; r, pleon. 



