MUSEUM OF COMPARATIVE ZOOLOGY. 289 



C. htmgarlcus on some occagions, and sometimes in specimens of Hlpponyx. 

 It may be a purely individual character, but is very regular, and therelure lias 

 been fully descriljed. 



This species recalls the C, ohliquus of the Craf^, and some of the species called 

 Brocchia from the Italian Tertiaries. Brocchia is always stated to be sinistral, 

 and the spire viewed from behind is certaiuly twisted to the left of a vertical 

 plane more than usual ; but I have yet to see a single specimen in which there 

 is a sinistral nucleus, or any genuine sinistrorsity of the rest of the shell. 

 Possibly such may exist, but I doubt it. 



Family AMALTHEIDyE. 



Genus AMALTHEA ScnuMAcnER. 



AmaUhea Schum., Essai, pp. 56, 181, pi. xxi. fig. 4, 1817. 

 Hipponyx Defrance, Bull, des Sciences, p. 9, 1819. 



Amalthea benthophila n. s. 



Plate XIV. Fig. 1 a-b. 



Shell stout, white, smooth, with a smooth straw-colored epidermis and a 

 coil of about two whorls; apex elevated, nucleus glassy, rather large, of about 

 one whorl ; surface smooth, often polished, showing only irregularities due to 

 growth and a few microscopic spiral scratches ; aperture subcircular, interior 

 white, glossy ; basal plate sometimes quite thin, as when the moUusk is seated 

 on a fiat stone or another Amalthea, or quite thick, as when it roosts on a 

 Cidaris spine. It is marked with two diverging impressions corresponding to 

 the position of the adductors. Lat. of aperture, 8.0; Ion. of aperture, 8.0; 

 alt, 6.0 mm. 



Habitat. Off Sand Key, dead, in 50 fms.; Station 146, off St. Kitts, in 245 

 fms., on flat stone; Station 150, near Nevis, in 373 fms., on shells; Station. 

 167, near Guadelupe, in 175 fms., on spines of Echini; Station 206, off Mar- 

 tinique, in 170 fms., on Echinus spines; Station 223, off St. Vincent, 146 fms., 

 on shells. Bottom temperatures 45° to 55° F. 



This species by its smooth surface is easily distinguished from any other. 

 The irregularities of the Echinus spines are not reproduced on the surface of 

 the shell, as its pedestal, secreted by the foot, covers all such inequalities. I 

 cannot help doubting if there is any such connection between the base and the 

 adductors as exists between the latter and the shell. The irregularities of the 

 specimens living on a smooth surface indicate that they are not absolutely 

 fixed to one spot, at least not more than Gadinia or Crepidula when young. 

 If the adductors were organically attached to the base, of course it would be 

 death to the animal to move. 



The young shells, to the number of twenty or so, are protected by the 

 mother, and attain a size of more than one whorl before leaving their capsules. 



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