of British Mollusca. 465 



Fam. Spirulidae. 



Three genera which Steenstrup regards as allied to Spirilla, 

 Sepiadarium, Sepioloidea, and Idiosepius, Steenstrup, have 

 no shell. Fischer places these genera in two families near 

 the Loliginida?. The hectocotylization of Idiosepius very 

 closely accords with that of the male Spirula australis 

 described by Owen ; both ventral arms are entirely or almost 

 entirely devoid of suckers, and one is of much larger siz'i 

 than the other. Steenstrup places the two groups Sepiadarii 

 and Ideosepii in his family Sepio-Loliginei, and thus defines 

 them : — > 



Group Sepiadarii. Fins narrow, occupying only smaller 

 portion of the length. No internal shell. Mantle 

 united to neck on the back. One of the fourth or 

 ventral arms hectocotylized. Genera Septiadarium and 

 Sepioloidea. 



Group Idiosepii. Fins small, terminal. Mantle supported 

 by cartilaginous prominence or ridge and correspond- 

 ing pit or furrow. Both ventral arms hectocotylized. 

 Genera Idiosepius, which has no internal shell, and 

 Spirula. 



Being unacquainted with the foregoing interesting genera, 

 I abstain from any conjecture as to their alliances. 



Class I. CEPHALOPODA. 

 Subclass DIBRANCHIATA. 



A. Mesaesenia. 

 Order I. OCTOPODA. 



Fam. 1. Octopidas. 

 Genus 1. Octopus, Lamarck. 



Sars thus describes the radula in this genus : — " Lamella? 

 radulse medians? magna?, acie in cuspidem recurvam longe 

 protractam exserta; laterales utrinque 2 valde ina?quales, 

 interior minima et rudimentaris, exterior magna, basi quad- 

 rangulari, acie unicuspidata ; uncini utrinque singuli, f alci- 

 formes, incurvi ; lamina? limbi magna?, quadrangulares. 

 Formula radula? 1— 1— (1 . 1) . 1 . (1 . 1)— 1— 1. 



Ami. <5 Maq. N. Hist. Ser. 6. Vol. v. 33 



