84 GASTEROPODA OF THE INFERIOR OOLITE. 



very limited extent — by the whorls of the spire presenting longitudinal ribs more 

 or less marked, cut by transverse striae, a strong keel, or at least a very pro- 

 nounced ' ressaut,' forming upon the whorl a ' meplat ' towards the suture, 

 which is deeply cut ; finally a body-whorl much more developed than the 

 others." 



It is somewhat difficult to understand on what grounds Fischer places this 

 genus under the Littorinidse, and yet in the so-called Purpurina Manor and its 

 allies there is a very strong resemblance to some sections of the numerously- 

 represented genus Amberleya (Eucyclus). On the other hand, Amberleya ornata, 

 D'Orb. (non Sow.), is very like a Purpurine, and was, in fact, recognised as such 

 by Oppel (' Juraformation,' p. 387), who records it from the Humphriesianns-zone 

 of Oeschingen, and also from the Bayeux beds. In well-preserved specimens of 

 Amberleya ornata, D'Orb., the anterior groove or incipient canal is as well marked 

 as in most Purpurines, and better perhaps than in the majority of specimens 

 obtained by collectors. Thus there is certainly a link between Purpurina and 

 Amberleya, though there may be no real affinity. Our difficulties are still further 

 increased by the fact that Fischer classes Amberleya under the Turbinidas. As 

 regards the so-called canal in Purpurina it may be seen to vary from a very strong 

 and well-defined channel with reflexed columella, such as those of P. aspera 

 (PI. I, fig. 11) and P. calcar (PL II, fig. 1), to the shallow, spoon-shaped grooves 

 of P. bellona (PI. I, fig. 5) and P. inflata (PI. II, fig. 2). It should also be remem- 

 bered that in the majority of specimens the anterior extremity has lost all original 

 character from wear, so that we are only now and again permitted to see what the 

 shell really was like. 



Distribution, fyc. — The duration of the genus appears to have been limited. 

 The oldest form known to us in England is P. ornatissima, Moore, said to occur 

 in the Marlstone of Ilminster (Moore, ' Middle and Upper Lias of S.-W. England,' 

 p. 89, pi. v, figs. 20, 21), where it is described as being very rare. There is a 

 somewhat similar form figured and described by Vacek (p. 53 (109), pi. 18, fig. 7) 

 as P. bellona, D'Orb., from the opalinus-zone of the subalpine region. Nowhere 

 are these pretty shells common, but in England they are the most abundant and 

 best preserved in the Inferior Oolite of Dorsetshire, where the Parhinsoni-zone of 

 Burton Bradstock yields for the most part different species to those characteristic 

 of the Sowerbyi-hed of Bradford Abbas. 



In the Inferior Oolite of the Cotteswolds Purpurina is rare, and usually in 

 such indifferent preservation that the finer distinctions, held to constitute specific 

 differences, can scarcely be made out. The same remarks apply for the most 

 part to the Lincolnshire Limestone and Yorkshire Dogger. On higher geological 

 horizons in England one species of Purpurina has been recognised in the Great 

 Oolite (Bathonian), and another species in the Cornbrash and Kelloway Rock of 



