MUSEUM OF COMPARATIVE ZOOLOGY. 61 



nal)le, it is probable that the species is tliat referred to by Dr. Oeorf^e Forbes 

 of Ikninida, in a letter to John Eaton Dodsvvorth, published in the Philosophi- 

 cal Transactions in 1758, and figured there.* 



As to tlie question whetlier tliis slicll (named from the above figures by 

 Morch Operculatum bermudense, Mai. Bliitt., XXII. p. 179, 1875) is distinct 

 from the Mediterranean species, this still remains io be investigated. 



Subgenus HYALOPATINA Dall. 

 Shell dextral, flattened, sculptured, ovate. Nucleus sinistral, immersed. 



Hyalopatina Rushii n. s. 



Shell oval, translucent bluish white, almost perfectly flat, extremely thin. 

 Nucleus of less than one whorl, half immersed, the remainder rising above 

 the surface, smooth, not polished. Upper surface nearly flat, except near the 

 nucleus which is situated nearly in the median line and close to the posterior 

 margin ; concentrically faintly undulated ; with faint concentric growth lines, 

 and with very numerous radiating lines of extremely minute slightly elevated 

 points, recalling the granules of Foromya on a much finer and more minute 

 scale. They are so small as to hardly appear elevated, but more like radiating 

 lines of opaque dots on the generally translucent surface. Margin regularly 

 ovate, entire, extremely thin. Under surface of shell mostly polished, a little 

 domed under the part in front of the nucleus ; there are faint markings (in- 

 terrupted on the right side about the middle) which appear as if they might 

 represent the area of muscular insertion, but the polish of the shell is such 

 that this is not definitely ascertained. The sides of the shell are a little ele- 

 vated, as if it had grown on a slightly concave surface, but the ends are de- 

 pressed about to the same extent. Max. long. 9.3 ; max. lat. 7.5; posterior 

 margin to nucleus, 1.8 mm. 



Habitat. Off Great Isaac Light, Bahamas, in 30 fms., Dr. W. H. Kush. 

 U. S. Nat. Mus. Coll. 61222. 



This remarkable shell has been some time in the National Museum and has 

 been submitted to several conchologists, and studied with much care. In the 

 absence of any further information, I have come to the conclusion that it may 

 be related to Umhraculum, from which, conch ologically, it is separated by its 

 oval form, posterior nucleus, and granulated surface. The discovery of a 

 living specimen, however, may show the true relations of the creature to 

 be elsewhere. It has a little the general appearance of an extremely thin, 

 flat Crepidula unguiformis without a deck, and with the nucleus within the 

 margin. 



* Plate XXXV. figs. 1, 2. 



