216 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 5 



service of the Direccion Forestal y de Caza y Pesca, Mexico, for whom I 

 take pleasure in naming it. Dr. Stansch secured 2cf from coral banks in 

 the vicinity of the lighthouse, Tres Marias Islands, and 1$ from oyster 

 beds at Teacapan, state of Sinaloa. Otherwise, the species is known only 

 from specimens collected by the Hancock Expeditions. 



Type: The second largest specimen, a female of 38 mm. in median 

 length exclusive of the 3 mm. rostrum, from Tangola-Tangola Bay, 

 Mexico, March 1, 1934 (Hancock Exped. Sta. 261-34), has been selected 

 as the type (U.S.N.M. No. 76355). 



Description: One of the Gonodactylus oerstedii-group with dorsally 

 spined or spinulose telson, but differing at once from its near allies by the 

 complete absence of spinules on the accessory carinae, by the unarmed 

 and relatively inconspicuous knob more or less underneath the hinder end 

 of the median carina, and by the fact that the intermediate carina nor- 

 mally and usually ends posteriorly in a single spine; rarely is the spine 

 terminating this carina followed by a second and smaller one. Occa- 

 sionally one or the other, more rarely both, of the accessory carinae show 

 one or two small nodulations, but never spines. 



Only the posterior portions of the submedian carinae are developed ; 

 they form, as it were, the flukes of the anchor of which the median carina 

 forms the stock (not so well marked as in some species) ; the median and 

 submedian carinae are posteriorly spined (the "anchor" is thus trispi- 

 nose) ; the spines terminating the submedian carinae are often strongly 

 exserted and upturned, while the median spine, always the larger of the 

 three, is inclined downward. The spines terminating the intermediate 

 carinae are typically larger and stouter than those on the submedian 

 carinae and about the size of the one arming the median carina. 



The submedian and intermediate marginal teeth of the telson are 

 well separated by a distinct notch, as are the corresponding teeth in 

 specimens of G. oerstedii with the typical Atlantic type telson. 



The crests or carinae of the submedian teeth of the telson are typically 

 armed with but a single spine; in perhaps a fourth of the specimens 

 there are 2 spines on one of a pair of submedian crests, the other having 

 but a single spine or the faint indication in one instance of a slight 

 nodulation, and in another 2. In all other specimens a single spine 

 armed this crest, paired in almost every instance with another single 

 spine on the corresponding crest of the opposite side of the telson; in 3 

 specimens one of these spines was represented by a small nodule, and in 

 only one specimen was there a nodule on each side instead of a spine. 



