66 



* C. EUROP^EA. C. Pediculus. Turt. Lin. Borlase's Nat. 

 Hist. Com., pi. 28, fig. 12. Stew. Elem., vol., 2, p. 397. 

 Mont. Test. Brit., vol. 1, p. 200. C. E. Flem. Brit. An., 

 p. 330. In its young state this is altogether unlike the 

 perfect shell, and constitutes the C. Bullata of Montagu, 

 Test. Brit., vol. 1, p. 202, pi. 6, fig. 1. In this condition 

 they differ greatly in size; but whatever be the magnitude 

 obtained, the further progress towards the perfect mark- 

 ings is not accompanied with enlargement.' so that many 

 matured shells are much smaller than others in their first 

 growth. When the form and striation are in the inter- 

 mediate state, they constitute the Gypraea Arctica of 

 Montagu, vol. 1, p. 201. These changes are rapidly 

 passed, and take place about the end of summer. Com- 

 mon, and often found with the animal, in crab-boats. 

 Cornish specimens are usually smaller than those farther 

 east. 



CEPHALOPODA. 

 POLYTHALAMOUS CEPHALOPODA. 

 The shell many chambered, more or less enveloped, placed 

 on the hinder part of the body of the animal,, often adhering. 



FIRST DIVISION. 



The shell many chambered, the partitions simple; not 

 showing any divided sinuous sutures on the inner surface of 

 the shell. 



ORTHOCERATA. 

 The shell straight or nearly so ; not spiral. 



ORTHOCERA. 



GENERIC CHARACTER: The shell straight or slightly 

 arched, subconical, striated on the outside by numerous 

 longitudinal ribs; chambers formed by transverse partitions, 

 perforated by a central or marginal tube. 



O. IMPERFORATA. Dentalium I. Turt. Lin. Mont. 

 Test Brit., vol. 2, p. 496. O. I. Flem. Brit. An., p. 237. 

 Found by Montagu in sand at Falmouth. 



O. RECTA. Nautilus Rectus. Mont. Test. Brit., vol. 1, 

 p. 197. O. R. Flem. BriU An., p. 236. Usually con- 

 sidered exceedingly rare ; but in a few instances I have 

 found it adhering to the shell of a Pinna from deep water, 

 and suppose it not uncommon, though from its small size 

 commonly overlooked. 



LJTUOLATA. 

 The shell partly spiral, the last whorl continuing in a 

 straight line. 



