DALL: MOLLUSCA ANT) BRACHIOPODA. 331 



to consider the formation of a new genus. The discovery of a similar base in a 

 living species H. " mitrata Gmelin " of Defrance i^H. antiquata Linne) confirmed 

 him in this opiuion, and lie proceeded to publish his new genus, leaving the other 

 species of Pileopsis Lamarck, which were believed to form no shelly base, to be 

 grouped separately. The shelly base alone might not be considered a sufficient 

 character to found a genus upon, but the wide differences of anatomy which are 

 claimed to exist between Capulus and Hipponix, if confirmed by more modern 

 examination, are of even more tliau generic importance. U. " mitrata " being the 

 first species in Defrance's list, might naturally serve as type, though the genus is 

 known really to have been founded on H. cornucopiae ; but as they are both with- 

 out any doubt congeneric, the question becomes unimportant. As Defrance in 

 using liis new name terminated his specific names in a, it follows that he regarded 

 the name as feminine, and subsequent writers should not try to alter tiiis on the 

 basis of an assumption. The smooth, deep-water species separated by Mr. Mel- 

 vill have a peculiar facies, but perhaps hardly of subgeueric value. The slight 

 importance of surface sculpture as iudicative of systematic differences of such 

 value is illustrated by the following species which unites in a single individual the 

 characteristics of two such discrepant species as H. antiquata and H. tubrufa 



Hipponix delicata Dall, n. sp. 



Shell solid, conical, the apex in the posterior third of the length, erect, blunt ; 

 the posterior slope steep, the anterior much longer, gentle, near the apex almost a 

 little concave ; sliell substance porcellunous, greenish-white, the muscular impres- 

 sions more translucent and darker colored; sculpture of the apical third concen- 

 trically lamellose, as in U. antiquata L., the remainder of the shell continuous 

 with irregular but not lamellar narrow waves, delicately, evenly, radiately grooved ; 

 interior polished, with a thick smooth peritreme. Alt. 5 ; Ion. 11 ; lat. 9 mm., 

 the apex 3.5 mm. in front of the posterior edge. 



U. S. S. "Albatross," station 3355, Gulf of Panama, in 182 fathoms, mud, 

 bottom temperature 54° F. U. S. N. Mus. 123,041. 



The curious combination of lamellose and radial sculpture, usually found in 

 different species, marks this one as unique. The radial striation is finer than in 

 any of the well-known shallow water species. The shell is fresh, tliough it did 

 not contain the animal. 



Hipponix barbata Sowerbt. 



Hipponyx harbatus Sowerby, P. Z. S. Lend., 1835, p. 5 ; Tlies. Conch., Brachiopoda, 

 p. 3G0, pi. 73, figs. 26, 27. 



Beach, Cliatham Island, Galapagos Islands, U. S. S. "Albatross." U. S. N. 

 Mus. 96,044. 



This species is widely distributed and is reported as far north as the Gulf of 

 California. 



