168 PROF. OWEN ON NEW AND RARE CEPHALOPODA. 
that of the modern Spirula to a coiled Ammonite (Am. leptophyllus, Bedwell) 4 feet 
in diameter ; and of the straight camerated kinds (Orthoceratites) Dr. Bigsby has noted 
a specimen of Huronia vertebralis 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. 
DESCRIPTION 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. 
Sepioteuthis brevis, Ow. 
Fig. 1. Ventral view, dissected, natural size. 
Sepiola oweniana, @Orb. 
Fig. 2. Male organs of generation, magnified. 
