100 K. J. Bush — Marine Gastropods referred to 



Delphinoidea Brown, 1827. Type, D. serpuloides (Montagu). Devonshire coast, 

 England. 



Plate XXII. figs. 1-16. 



" Spire depressed, surface smooth, divested of spinous processes ; 

 aperture orbicular, or nearly so, and not enveloping the body volu- 

 tion." 111. Cat. Gt. Britain, p. 19, 1838? (2d ed.) 



This genus has been considered by most authors as a synonym of 

 Cyclostrema, but the very small, nearly smooth species referred to it 

 by Brown are very unlike the highl}^ sculptured type of that genus. 



Even as restricted and described in the 2d ed. this is a hetero- 

 genous genus without a designated type, with two subdivisions 

 (I. — Volutions Dextral. II. — Volutions Sinistral), containing in all 

 four described and figured species, in the following order : 



1. D. unispiralis (Montagu). 2. D. depressa (Montagu). 3. D. 

 serpxdoides (Montagu), and 4. D. resupinata (Montagu). The last 

 being the only representative of the second subdivision. 



These with several other of Montagu's species of Helix were 

 included under Delphinoidea in the 1st ed., 1827. The first species, 

 unispiralis, is described by Brown as follows : 



" Shell glossy white and opaque, with one volution, umbilicate on 

 both sides ; aperture circular. Diameter scarce a line." 



" Found at Sandwich, and is v»ery rare." 



This was without doubt a veliger shell, the true specific relations 

 of which it is impossible to determine without comparing it with 

 similar species from the same region. 



Fleming, m 1828' (Hist. Brit, An.), constituted the genus Skenea 

 and referred depressa Montagu, and serpuloides Montagu, to it. 

 In the 2d ed. Brown restored these two species to his genus Delphi- 

 noidea and gave references to Fleming's article. Helix depressus 

 Montagu is now considered the same as Skenea planorhis (Fabricius)," 

 which stands as the type of Skenea. See plate xxiii, figs. 5, 8, 8«. 



1 Gray, P. Z. S., 1847, p. 152, gives 1824. 



'^ Skenea planorhis (Fabricius) is common on the rocky shores of our eastern coast 

 from Long Island to Greenland. It is a minute shell without sculpture, covered with 

 a conspicuous amber or delicate horn-colored epidermis, of about three well-rounded 

 whorls, with deep sutures, coiled nearly in the same plane so that the spire is but 

 little elevated. The umbilicus is large, revealing all the whorls, with rounded walls. 

 Aperture circular; peritreme simple, continuous. Operculum thin, of a delicate horn- 

 color, circular, with central nucleus of about six whorls defined by an indistinct spiral 

 line. Radula with a series of seven unequal, distinctly serrate, curved teeth in each 

 row. For figures see G. 0. Sars, Moll. Reg. Arct. Norv., pi. vi, f. 15; pi. xviii, f. 23, 

 1878. 



