168 PEOF. OWEN ON NEW AND EAEE CEPHALOPODA. 



that of the modern Spirula to a coiled Ammonite {Am. le])tofhyllus, Bedwell) 4 feet 

 in diameter ; and of the straight camerated kinds (Orthoceratites) Dr. Bigsby has noted 

 a specimen oi Huronia vertehralis in the cliffs of Drummond Island 6 feet in length. 

 The constructors and occupants of such shells may have approached in size to the 

 larger naked Cephalopods recorded in the present paper. 



DESCEIPTION OF THE PLATES. 



PLATE XXIII. 

 Tritacceopus cornufus, Ow. 



Fig. 1. Dorsal view, three quarters natural size. 

 Fig. 2. Oral environment, one quarter natural size. 



PLATE XXIV. 



Sepia palmata, Ow. 



Fig. 1. Dorsal view, natural size. 



Fig. 2. Sepium or " cuttle-bone," natural size. 



PLATE XXV. 



Seina pahnata, Ow. 



Fig. 1. Ventral view, natural size. 

 Fig. 2. Sepium, natural size. 



PLATE XXVI. 



Sepioteutliis brevis, Ow. 

 Fig. 1. Ventral view, dissected, natural size. 



Sepiola oiveniana, d'Orb. 

 Fig. 2. Male organs of generation, magnified. 



