72 PROVISIONAL AID TO THE STUDY OF TASMANIAN MOLLUSCA. 



broad, flat, thickened internally by numerous plates, 



terminating behind in a hollow, imperfectly chambered, 



apex or mucro, without connecting siphon. 



Genus. 

 A lid-like fold under the eyes with 



lachrymal openings over them; 



six aqueous pores in the buccal 



membrane ; arms short ; tentacles 



long, suckers long, pedunculated ; 



siphon with very large valve ; 



fourth left arm hectocotylised to 



its base, (one or two species 



undetermined abundant in Tas- 



manian waters) Sepia ( ) 



Differing from Sepia by the sessile 



arms having only two rows of 



suckers Hemisepius (— ) 



(v.) Family Spieitmdjs. 



Animal, body oblong, with minute terminal fins ; mantle 

 supported by a cervical and two ventral ridges and 

 grooves; arms with six rows of minute cups; tentacular 

 arms elongated ; siphon valved ; shell laxly spiral, 

 pearly whorls on the same plane, not in connection, 

 chambered ; chambers connected by a ventral siphon, 

 invested by a series of cone-shaped tubes, one for each 

 chamber ; shell is placed vertically in the end of the 

 body, and is held in place by side flaps of the mantle. 



Characters same as those of family Spirula (7) 



(B.) Teteabbanchiata. 

 Animal breathing by two pairs of symmetrical branchise ; 

 eyes pedunculated; mandibles shelly ; arms very 

 numerous, without suckers ; shell external, chambered - 

 capable of containing the animal. 



(vi.) Family Nautilid^. 



Septa simply curved, concave on the outer face; sutures 

 simple, or undulate, or lobed ; mouth simple ; siphonal 

 opening nearly central ; shell often banded with colour 

 pearly inside. (Six living, and over 2,000 fossil species.) 



Shell involute, discoidal few-whorled; 

 septa concave, simple ; siphuncle 

 nearly central. Dist. — Tropical 

 seas. Australia and Tasmania Nautilus (8) 



