Cyclostrema, Adeorbis, Vitrinella, and related genera. 101 



The animal of serpuloides was carefully studied and described by 

 Wm. Clark in 1855 (Brit. Mar. Test, Moll.), and the species was 

 placed by him in the genus Trochus. A figure of it was given by 

 H. and A. Adams in 1858 (Gen. Rec. Moll.), under the name Cyclos- 

 trema serpidoides, but these authors stated that " Should the smaller 

 British species require to be separated from the more typical forms 

 they will take the name of Delphinoidea Brown." Jeffreys, in 1865 

 (Brit. Cone, iii.), described and figured it as Cyclostrema serpu- 

 loides because " Delphinoidea is both superfluous and heterogenous." 

 This decided statement has doubtless been the cause of much of the 

 misunderstanding of Cyclostrema of more recent authors. G. O. 

 Sars in 1878 (Reg. Moll. Arc. Norv.), restored the species to Delphin- 

 oidea, but desci'ibed and figured the young of Margarita helicina 

 (Fab.) as serptuloides (Supl., p. 346). 



Delphinoidea is unquestionably a very unfortunate selection for a 

 genei'ic name, as it is used to designate an ordinal group of Dol- 

 phins, etc. 



Delphinoidea Brown (sens, restr,). 



Shell small, white, consisting of a few convex whorls coiled nearly 

 in the same plane so that the spire is but little raised ; suture deep ; 

 umbilicus rather large, deep, with rounded walls, showing all the 

 whorls, and not defined by a carina ; aperture oblique, nearly cir- 

 cular, slightly angulated above, not modified by the body -whorl ; 

 peritreme simple, thin, entire, but slightly attached ; columellar edge 

 very slightly or not at all flattened. 



Type, D. serpidoides (Montagu). Described and figured by Jef- 

 freys, B. C, iii, p. 290, pi. vii, f. 3. 



Specimens (No. 9450) from Guernsey, England, in the Yale 

 Museum, presented by the Rev. Canon A. M. Norman, measure about 

 j.gmm jjj (Jiametcr. They are rather thin, white, somewhat shining, of 

 about three convex whorls, forming a very low spire with deep 

 sutures. Very fine microscopic, raised, revolving lines commence on 

 the periphery of the whorls ; these become more conspicuous and 

 widely separated on the base and umbilical region. The aperture is 

 nearly circular, with a slight angle where it touches the body- whorl. 

 The peritreme is simple, continuous, but along the columellar mar- 

 gin the edge seems slightly flattened. Some specimens have a deli- 

 cate raised line just within the aperture. 



