THE SPIDER CRABS OF AMERICA 547 



KEY TO THE SPECIES OF THE GENUS MESOKHOKA 



A*. Movable finger vertical, without smooth bead granule. Branchial ridge 

 nearly straight sexspinosa, p. 547. 



A^. Movable finger oblique, with smooth bead granule on outer surface. Bran- 

 chial ridge curved bellii, p. 548. 



Analogous species on opposite sides of the continent: sexspinosa 

 (Atlantic) ; hellii (Pacific) . 



MESORHOEA SEXSPINOSA Stimpson 



Plate 200 



Mesorhoea sexpinosa Stimpson, Bull. Mus. Comp. Zool., vol. 2, 1871, p. 136 



(type-locality, 4 miles southwest of Loggerhead Key, 11 fathoms; type 



not extant). 

 Solenolambrus fastigatus A. Milne Edwards, Crust. R^g. Mex., 1878, p. 



163, pi. 29, figs. 5-5e (type-locality, Mexico (Gulf of Mexico on plate); 



type in Paris Mus.). — A. Milne Edwards and Bouvier, Mem. Mus. 



Comp. Zool., vol. 47, 1923, p. 357. 

 Mesorhoea sexspinosa A. Milne Edwards, Crust. R^g. Mex., 1878, p. 164. 

 Solenolambrus typicus Rathbun, Bull. U. S. Fish Comm., vol. 20, for 1900, 



pt. 2 (1901), p. 81 (part: specimen from Punta de Melones). 



Diagnosis. — Carapace one-fifth or one-fourth broader than long. 

 Branchial ridge nearly straight. Cardiac spine the most slender. 

 Movable finger vertical, without smooth bead granule. Outer angle 

 of wrist laminate. 



Descri'ption. — Carapace about equally produced in front and 

 behind, beyond the line of the lateral angles. Surface punctate 

 and inconspicuoush' pubescent. Protuberances of gastric, cardiac 

 and branchial regions strongly angular, each surmounted by a three- 

 sided spine, the branchial spine being situated on the postero-lateral 

 margin, of which it forms a projection. Angles or ridges more or 

 less crenulated. Lateral edges of gastric protuberance continued 

 forward nearly to front, becoming parallel shortly after diverging 

 from the spine. Cardiac spine more slender than the others, its 

 posterior edge nearly vertical. Branchial ridge nearly straight. 

 Between protuberances and ridges the surface is more or less reg- 

 ularly concave, the sides of the protuberances not being swollen. 

 Rostrum short. Margins of carapace sublaminiform and almost 

 entire, the normal crenulation being indicated only by faint im- 

 pressed lines; microscopic notches may, however, be detected on 

 antero-lateral margin which is slightly convex toward lateral angle. 

 Postero-lateral margin concave. Posterior margin about half as 

 long as postero-lateral, convex at middle, terminating on either side 

 in a slight tooth. Afferent channels deep, separated from the 

 subhepatic channels by a very thin and sharp, prominent, ciliated 

 lamina, and defined on the inner side by the ciliated outer edge of 

 ischimn of outer maxillipeds. From anterior angle of buccal area a 



