26 ACANTHOCHITES. 



furnished with an elegant pattern of sphreroidal tubercles and chains 

 of granules in lines diverging from the ridge. Posterior valve hav- 

 ing the mucro subcentral and subconspicuous. 



Interior roseate or white ; the acute and lobed margins of the 

 valves not separated, large, with a single slit on each side, the lobes 

 angulate ; sinus large, flat ; very delicately wrinkled in the cavity 

 of the ridge, laminated under the beaks. Posterior valve hexagonal, 

 with two posterior slits. 



Girdle copiously adorned with translucid, erect spicules, and at 

 the front and hind ends and sutures having tufts of spicules or 

 needles. ( Cpr.) 



Length 4, breadth Ij, alt. i mill. 



Mazatlan, on Spondyhi,s calcifer (Liverpool Coll.) 



Acanthochites arragonites Cpr., Catal. of Mazatlan Shells, p. 198 

 (1857.) 



Whether the varied coloring of this shell, its elegant sculpture, 

 the bird-like form of the medial or hexagonal shape of the bifissured 

 terminal valves, or the adornment of the mantle with the transparent 

 needle-like hairs, rising now in tufts, now in irregular crystals, be 

 examined under the microscope, it would be difficult to find any 

 shell of such surpassing beauty. Only one perfect specimen was 

 found, but fresh valves belonging to several other individuals were 

 detected among the Spondylus washings. The valves in the same 

 shell greatly differ in color as in L. albolineatus. The posterior 

 valve is peculiarly exquisite in its form, color and sculpture. There 

 is considerable variation in the size of the tubercles and in the stria- 

 tion of the jugum. ( Cpr.) 



A. RHODEUS Pilsbry, n. sp. PI. 12, figs. 48, 49, 50, 51. 



Oblong, the exposed portion of the valves about one-third the 

 entire width of the animal. Valves depressed, obtusely carinated, 

 brown, the eroded apices roseate. 



The intermediate valves appear almost separated by the encroach- 

 ment of the girdle at the sutures; a heart-shaped or subtriangular 

 area remaining exposed. Dorsal band sharply defined and strongly 

 differentiated from the side areas, very narroiv, shining, having slight 

 growth-lines but no longitudinal strice. Latero-pleural or side areas 

 sculptured tvith rounded-oval concave-topped elevations arranged in 

 rows subparallel to the ridge, becoming radial and then irregular at 



