MOLLUSCA. 13 



recollected that these writers had the authority of Cuvier 1 for continuing to associate 

 together Cephalopodic animals with shells so similar in their complex chambered structure, 

 as those of the Nautilus and Spirula. But at the same time I retained all my convictions 

 that the period woidd arrive when it should be demonstrated that a Cephalopod with arms and 

 peduncles, like those of a Sepia, would have the same type of Cephalopodic organization as 

 the Sepia : a type so modified from that of the many-armed Nautilus as to forbid their 

 association in the same Order in any system professing to be based on Nature ; i. e. on the 

 totality of the organization of its objects. 



The chief addition made by M. de Blainville's Memoir of 1837 to the knowledge of 

 the exterior characters of the Spirula was the existence of a circular disc with a pair of 

 fin-like appendages (" aplatissement oblique au milieu duquel est un bouton terminal, accom- 

 pagne a droite et a gauche d'une petite nageoire demi-circulaire," I.e. p. 376. see fig. 15*, ac. 

 in pi. iv.) at the posterior end of the body, covering and concealing the part of the last whorl of 

 the shell which winds round that end, and which whorl was exposed in Lamarck's and Peron's 

 specimen (fig.l*) as it is Sir Edward Belcher's (fig. 7). The same disc, with rudiments of the 

 terminal fins or appendages, is present in Mr. Cuming's perfect specimen (fig. 8, ac). The 

 disc is called "a thick gland" by Mr. Gray (I.e. p. 259), and a "leathery gland" by 

 Mr. Reeve (1. c. p. 16); but the texture of the part is not described by either author. 

 It remains to be seen whether this appendage be truly constant in nature, or whether 

 it be characteristic of age, or sex, or species. Mr. Gray in his brief notice of some of the 

 exterior characters of Mr. Cuming's specimen of Spirula, affirms that "it differs from 

 the Cuttle-fish in being entirely destitute of any fins" (torn. cit. p. 258. 2 ): but Mr. Reeve, 

 by a more accurate observation of the same specimen, confirms M. de Blainville's descrip- 

 tion of two terminal and lateral fins to the Spirula ; stating that " they are clearly definable, 

 one at each lateral extremity, on either side of the terminal gland" (1. c. p. 18). Their 

 condition is accurately given in the figure representing the hind end of Mr. Cuming's Spirula 

 (pi. iv. fig. 8, ac ac). With regard to the structure of the intervening subcircular disc (ad), 

 I could not detect any trace of the pores of glands upon its surface, and the structure of the 

 same part in the mantle of the Spirula reticulata (fig. 3 and 9) was that of condensed cellular 

 tissue only. This I determined by microscopical examination. The central orifice {ad, fig. 9) 

 leads merely to the interspace between the disc and the last whorl of the shell, and is not the 

 excretory outlet of any glandular cavity. In the specimen of Sp. reticulata which consisted of the 

 mantle only, with its terminal appendage and the shell, the latter, by the violence that has torn 

 away the head and viscera, has been displaced and turned half round with the open end of the 

 last whorl projecting through the ventral aperture (fig. 3, fm). The lateral fin-like appendages 



1 Kegne Animal, vol. iii. (1830) p. 17. "Des Nautiles. — "Une d'elles appartient en effet a un Cephalopode 

 tres semblable a une seiche, mais a bras plus courts ; e'est le genre Spirula, Lam." 



2 Mr. Gray, however, after having been made acquainted with M. de Blainville's Memoir, corrects his error in a 

 supplementary note in a subsequent number of the Annals (p. 415). 



E 



