172 MANUAL OF THE MOLLUSCA. 



Ommastrephes, D'Orbigny. Sagittated calamary. 



Etymology, omma, the eyes, and strepho, to turn. 



Synonym, Hyaloteutliis (Grray). 



Type, O. sagittatus, Lam, 



Body cylindrical ; terminal fins large and rhombic. Arms 

 with two rows of suckers, and sometimes an internal mem- 

 branous fringe. Tentacles short and strong, with four rows of 

 cups. 



Pen consisting of a shaft with three diverging ribs, and a 

 hollow conical appendix. Length from one inch to nearly four 

 feet. 



The sagittated calamaries are gregarious, and frequent the 

 open sea in all climates. They are extensively used in the cod- 

 fishery off Newfoundland, and are the principal food of the 

 dolphins and cachalots, as well as of the albatross and larger 

 petrels. The sailors call them " sea-arrows," or " flying squids," 

 from their habit of leaping out of the water, often to such a 

 height as to fall on the decks of vessels. They leave their eggs 

 in long clusters floating at the surface. 



Distribution, 14 recent species ; similar pens (4 species) have 

 been found fossil in the Oxford clay, Solenhofen ; it may, how- 

 ever, be doubted whether they are generically identical. There 

 is 1 tertiary species. 



Thysanotetjthis, Troschel. '"1857. 



Etymology, thysanos, a fringe. 



Arms sessile and webbed, but without hooks. Tentacles fur- 

 nished with cups. Fin long. Pen sagittate. Two recent 

 species, T. rhombus, T. elegans. Mediterranean. 



LOLIOLTJS, Stp. 1856. 



Pen horny, broad, with the shaft sharp-keeled ; no muscular 

 bands to the funnel ; suckers with a raised band. Left fourth 

 arm hectocotylised. 



Distribution, 2 species. Indian Ocean. 



Plesioteuthis, "Wagner. 1860. 



Pen slender, with a central and two side ridges. Point 

 arrow-shaped. Arms with hooks. 

 Distribution, 2 species. Lias. Solenhofen slate. 



