60 FAUNA OF THE CORNBRASH. 



species is shorter it is also much narrower, so the proportion is 10. This is its 

 next successor in the Kelloway rock. 



Distribution. — All the known specimens (two in the Sedgwick Museum and two 

 fragments in the York Museum) are from the clay at Cayton Bay. 



GASTEROPODA. 



The remains of Gasteropoda in the Cornbrash are not numerous, and afford 

 little scope for any general observations. It must be borne in mind, however, that 

 we are dealing now with a group which contains both recent and fossil members, 

 and the classification and corresponding nomenclature are to a large extent derived 

 from the former by the consideration of parts not observable in the latter. In such 

 a case the placing of any fossil in a family or genus not founded on positive shell 

 characters may be a matter of un verifiable opinion. They may be treated of 

 accordingly in the order and under the families adopted by Hudleston in his 

 memoir on the Inferior Oolite Gasteropoda. 



Fa mily Apoee h a'i'd/E. 

 Genus ALARIA, Morris and Lycett. 



The records of Alaria are as follows : 

 A. bispinosa (6, 28). 

 *A. bispinosa var. elegans (50). *A. myurus var. teres (50). 

 *^4. hamus var. phillipsii. A. trifida. 



The early entry of A. bispinosa indicates only a member of that group. The 

 variety elegans is taken here to be a distinct species described as A. bicornis (see 

 p. 63). A. hamus var. phillipsii is taken to represent A. eomposita (see p. 64). 

 A. myurus var. teres is described under the name A. erinacea (see p. 61). The 

 specimen recorded as A. trifida is not well preserved, but has no relation to 

 Phillips' species, and, like some other specimens, suggests an Aporrhais. 



The species of Alaria depend on (1) the nature of the wing. (2) the ornament 

 of the spire. The latter feature divides them into groups, the former separates 

 species within those groups. The groups are those ornamented (a) with simple 

 lines, (b) with a median spiral keel, or (r) with longitudinal ribs. 



(a) Spire with simple lines ("Myurus group," Hudleston). 



