W. H. Hudlesion — Gasteropoda of the Portland Rocks. 389 



2. PsEUDOMELANiA ? PERciNCTA, sp.n. Plate XI. Figs. 2a, 2&. 



Description. — Specimen from the Cyrena-hediS of Alford Quarry, 

 near Tisbnry. 



Length (restored) 43 miUiiiietres. 



Width 24 



Length of last whorl to entire shell 60 : 100. 



Spiral angle 62°. 



Shell oblong, angular, not umbilicated. Three whorls and part of 

 a fourth remain ; the complete number would be about six. Spire 

 moderately elevated, with, probably, a fairly acute apex. Whorls 

 veiy angular, the posterior border being channeled, though not 

 deeply. Sides of the whorls almost flat, with a tendency towards 

 hollowing out in the anterior ones ; slope of each whorl regular and 

 nearly in accordance with the spiral angle. In the posterior whorls 

 the median keel is probably concealed by overlap, but it is very 

 characteristic of the body-whorl, which occupies about i-^ths of the 

 spire. Entire shell smooth, as far as can be learnt from its present 

 condition ; aperture oval, and somewhat elongate, and but moderately 

 excavated in the columellar region. Shell substance thick. Hardly 

 a trace of an umbilical groove. 



delations and Distribution. — It is perhaps more difficult to fix the 

 generic position of this peculiar shell than of the preceding species. 

 It has strong affinities with a well-known form which occurs in the 

 Dogger and Scarborough Limestone (Inf. Ool.) originally figured by 

 Phillips (G.Y. pi. iv. fig. 29) as Pliasianella cincta, and afterwards 

 described by Morris and Lycett (Ool. Mol. p. 113, pi. xv. fig. 20) as 

 Natica? (Euspira) cincta. We are apt to regard Euspira as a sub- 

 genus of Natica, yet neither this nor Phillips's species has the 

 semilunar aperture of that great group. A more remotely-allied 

 form, with a shorter spire, has been described from the Lias of 

 Eedcar by Tate and Blake (Yorkshire Lias, p. 349, pi. x. fig. 13), as 

 Natica purpuroidea, " which is evidently congeneric with Ampullaria 

 angulata, Dunk., quoted by Brauns under Purpurina." 



Such forms seem to have affinities on the one hand with the 

 Naticas, but yet more strongly with the so-called Phasianellas, 

 Chemnitzias and Pseudomelanias, and only await further recognition 

 to be placed in a distinct genus, whose appearance may probably be 

 held to indicate partly estuarine conditions. Throughout the long 

 interval between the Scarborough Limestone and the Portlandian no 

 such form is known to me in the Jurassic rocks of this country ; 

 but, after making due allowance for differences of mineralization, 

 one might be disposed to admit such a shell as Natica Beangrandi, 

 Lor. (Jurass. Sup. de Boulog., vol. i, j), 92, pi. viii. fig. 22), from the 

 Upper Portlandian of La Creche, into the group. 



3. PsEUDOMELANiA EUGosA, sp.n. Plate XI. Figs. 6«, &h. 



Description. — Specimen from the " creamy limestones " near 

 Aylesbury, Bucks. 



Shell oblong, angular, rugose, not umbilicated. The spiral angle 

 is between 70° and 75°, but the spire itself is too much injured for 



