196 W. S. Hudleston — On the TorlcsMre Oolites. 



On the other hand, P. elaborata from the Great Oolite of Minchin- 

 hampton has the longitudinal costae rather bolder and wider apart. 



3. — PuRPURiNA coNDENSATA, Heb. and Deslongch. 1860. Plate V. 



Figs. 3a, 3b. 

 " Turbo liratics," Bean MS. 



1860. Furpurina condensata, Heb. and Desl., Foss. de Montreuil-Bellay, p. 26, 

 pi. i. fig. 8 a-d. 



Bibliography, etc. — The authors describe their species as being 

 nearly related to other Purpurinas from the Callovian of Montreuil- 

 Bellay, which seems to be as rich in this peculiar group as the 

 Inferior Oolite of the Anglo-Norman basin. 



Description. — Specimen from the Kelloway Eock of Scarborough 

 (zone 5). Bean Collection, Brit. Mus. 



Only three whorls of this specimen are left. The ornaments are 

 faint, owing to its being almost in the condition of a cast. As far as 

 one can judge under these circumstances the longitudinal [i.e. trans- 

 verse of some) ribbing is somewhat similar in character to the 

 Inferior Oolite species (Fig. 2), and similarly decussated. But the 

 intercostal spaces are wider, and the whole form is on a much 

 grander scale. As there is no shell covering the columellar region, 

 the appearance of an umbilicus is stronger than usual in Purpiirina, 

 where a slight umbilical slit alone is visible. For the same reason 

 the slight anterior channel, only seen in well-preserved specimens, 

 is not visible in this instance. 



Belations and Distribution. — This form also occurs in theCornbrash 

 of Scarborough, and has usually been quoted in the lists as Turbo 

 elaboratiis. Decidedly scarce in both formations. It is obviously 

 related to some of the varieties of P. condensata, Heb. and Desl., 

 distinguished from the other Purpurinas by the stoutness of the costge, 

 and may perhaps be regarded as its representative in the Callovian of 

 Yorkshire. Some might prefer to describe the shell as a large form 

 of P. elaborata, from which in all probability it was descended. 

 Genus Natica. 



The species included below in this genus might in some cases be 

 referred to Euspira, Ag., in others to Littorina, but on the whole it 

 seems best to describe them under Natica ; the more so that the 

 genus Euspira of Agassiz has, it seems to me, been applied in a 

 somewhat opposite sense b}'- different writers. 



Besides the species enumerated, there are other forms, principally 

 from zones 1, 2 and 3, which might perhaps be entitled to specific 

 distinction — small ill-preserved specimens which one hardly knows 

 how to treat. 



In Yorkshire the genus is fairly represented in the lower beds 

 of the Inferior Oolite, though, with one remarliable exception, the 

 forms are small. In the " Cornbrash " and Oxfordian generally the 

 forms are very small, and not numerous, but in the Coral Eag 

 Natica revives in great force (see Corallian Gasteropoda).^ 



1 A small Natica is described by Lycett from the Cornbrasb, -which I cannot find 

 in any collection. As it may be necessary to publish a supplemental plate at the end 

 of this Memoir, further reference is deferred. 



