168 PEOF. OWEN ON NEW AND EAKE CEPHALOPODA. 



that of the modern Spinila to a coiled Ammonite {Am. leptopliyUus, Bedvvell) 4 feet 

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

 a specimen of Hwonia vertehraJis 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. 



Tritaxeopus cornutus, 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. 



Sepia palmata, Ow. 



Fig. 1. Ventral view, natural size. 

 Fig. 2. Sepium, natural size. 



PLATE XXVI. 

 Sepioteiithis brevis, Ow. 

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



Sepiola oiveniana, d'Orb. 

 Fig. 2. Male organs of generation, magnified. 



