458 Rev. Canon Norman's Revision 



furnished with suckers surmount long stalks ; these are the 

 Decapoda (or Decacera). 



D'Orbigny arranged the Decapoda in two groups — 



Oigopsides, in which the eyes have the crystalline lens 

 unprotected by any special membrane, so that they are in 

 immediate contact with the water. 



Myopsides, in which the crystalline lens is protected from 

 immediate contact with the water, being covered by a trans- 

 parent membrane continuous with the orbital cartilages. An 

 eyelid below the eye. 



Gray and Fisher arranged this order by means of the 

 differences of the shell — 



Chondropliora. — Shell corneous, thin, gladius-shaped or 

 lanceolate, a " pen." 



Sepiophora. — Shell calcareous, spongy, laminar, a " cuttle- 

 bone." 



Phragmopliora. — Shell calcareous, consisting of a number 

 of air-chambers connected by a siphonal tube. 



D'Orbigny's arrangement from the first was never received 

 with much favour. But when, in the early investigations on 

 hectocotylization, or the sexual modification of one of the arms 

 in the male Cephalopod, this hectocotylization had been 

 observed by Steenstrup in the various families of Myopsides, 

 but not at all in the Oigopsides, he was led in his admirable 

 paper on the subject * to regard that absence as proof of the 

 wisdom of d'Orbigny's classification, and wrote " This sum- 

 mary " (of hectocotylization in the various genera) " furnishes 

 a very striking evidence that there must be something natural 

 in d'Orbigny's division of the Decapod Cephalopoda into the 

 two principal groups ' Myopsides ' and ' Oigopsides,' although 

 no great inclination to adopt them has hitherto been shown. 

 The difference in the conditions of reproduction shows espe- 

 cially that the genus Ommatostrepkes, d'Orb., is still more 

 entitled to be removed far from the genus Loligo, with which 

 even modern malacologists, such as Verany and Troschel, 

 persist in placing it." But all this is changed. The male 

 of Ommatostrepkes and its allies are described, and the males 

 of other species of the Oigopsides are known. As far as thus 

 known they closely conform in the hectocotylization of one 

 of the ventral arms to this character in the genus Loligo. 

 Moreover, it would now seem that the Oigopsid eye is not con- 

 fined to the group Oigopsides, for Verrill has described a genus 

 Stoloteuthis f which, though it is said in general characters to be 

 closely allied to Sepiola, has this peculiar feature. He writes : — 



* See translation, Ann. & Mag. Nat. Hist. ser. 2, vol. xx. (1857), p. 81. 

 f Verrill, Trans. Connect. Acad. Sci. v. (1881), p. 417. 



