DIBRANCHIATE CEPHALOPODS. 



295 



mantle. This family includes the living Poulpes and their 

 allies, but has no fossil representatives. 



SECTION B. DECAPODA. The Cuttle-fishes of this section 

 have eight " arms " and two additional "tentacles/' which are 

 much longer than the true arms, and carry suckers on their 

 extremities only, which are expanded and club-shaped. The 

 suckers are pedunculated, the body is furnished with lateral 

 fins, and the shell is always internal. 



FAM. 3. TEUTHID^E. Shell consisting of an internal horny 

 "pen" or "gladius," composed of a central shaft and two 

 lateral wings. Several of such pens may exist in a single 

 individual, packed one behind the other. Fins mostly ter- 

 minal and angular. This family comprises the living Cala- 

 maries and Squids, and the following fossil genera have been 

 founded upon " pens " which have been discovered in various 

 Secondary deposits. 



a. Teudopsis. Pen lanceolate, produced in front, dilated and 

 spatulate behind. Five species of this genus have been de- 

 scribed from the Lias. 



b. Beloteuthis. Pen lanceolate, pointed in front, with two 

 small wing-like expansions behind (fig. 264). Six species have 

 been described by Count Minister from 



the Upper Lias of Wiirtemberg. 



c. Leptoteuthis. Pen horny, hastate, 

 broad in front, pointed behind. A single 

 species is known from the Oxford Clay 

 (Jurassic). 



d. Besides the above, remains found 

 in the Jurassic Rocks have been referred 

 to the living genera Enoploteuthis and 

 Ommastrephes ; and the extinct genus 

 Acanthoteuthis has also been placed in 

 this family. 



FAM. 4. SEPIAD^E. Internal skeleton 

 in the form of a broad, laminated, calcare- 

 ous plate, with an imperfectly-chambered 

 apex (or " mucro "). The chambered 

 portion of the skeleton corresponds with 

 the " phragmacone " of the Belemnites. 

 The fossil species of this family range from the Middle Oolites 

 upwards, and belong to the following three genera : 



a. Sepia. Shell broad and thick in front, laminated, and 

 terminating in a prominent mucro. The fossil forms belong 

 to the Oxford Clay (Jurassic) and Eocene Tertiary, and the 

 genus attains its maximum at the present day. 



Fig. 264. Belotenthis sub- 

 costata. Jurassic (Lias). 



