of British Mollusca. 463 



The Opistharsenia show many approaches to the Octopoda. 

 1st, the lateral arms of the male have enlarged suckers : 2nd, 

 the body is short and ovate ; 3rd, the fins almost invariably 

 hold quite a different position from that assumed by them 

 in the following suborders, being situated in the middle of 

 the sides as in some Octopods ; 4th, the shell is usually thin, 

 corneous, narrow, and not more than half the length of the 

 body, but is wholly absent in certain genera *. 



The tentacular arms are retractile into cavities. The 

 spermatophores are deposited at the orifice of the oviduct of 

 the female. The formula of the radula is 2 — 1 . 1 . 1 — 2. 

 Eggs isolated, though deposited in many gelatinous masses, 

 each mass containing a large number of eggs. 



Fam. Sepiolidse. 



Suborder II. PROSTHARSENIA f. 



Hectocotylization of one of the fourth, i. e. ventral arms. 



Section 1. ANOPROSTHARSENIA %. 



In this section the terminal portion of the arm is that 

 affected by hectocotylization, more rarely the entire arm 

 undergoes modification (genus Loliolus). Body much pro- 

 duced, more or less cylindrical; fins at more or less of the 

 hinder portion of the sides of the body and reaching its termi- 

 nation, or, if the body stretches beyond them, it is only as 

 a pointed extremity. Shell internal, horny, thin, gladius- 

 formed, or lanceolate. 



Tribe 1. Oigopsida. 



Eyes with a wide opening, through which the crystalline 

 lens may project and be in immediate contact with the 

 water. Spermatophores (in Ommastrephidce) deposited in the 

 branchial cavity of the female near the root of the gills. 

 Formula of the radula usually 1 — 2 — 1 . 1 . 1 — 2 — 1. The 

 middle and first laterals tricuspid, the outermost a very small 

 quadrangular plate (but in the genus Gonatus there are only 

 five teeth) . 



* Stauloteuthis and Inioteuthis, Verrill. 



t Trpoadios, in front, apa-rjv, male, in reference to the male having the 

 fourth or front arm hectocotylized. 



t ava>, from above, having the distal portion of the arm sexually 

 affected. 



