hitrodudioii to Animal Morphology. 325 



gills four; tentacles numerous; ink-bag none; epipodiallamellae 

 convolute with ununited edges ; eyes stalked ; mantle attached 

 annularly to the shell. There is one living genus, Nautilus, 

 the type of the family Nautilidae, whose septa are simply 

 curved ; of the fossil genera, ten belong to the same family, 

 and eighteen to the family Ammonitidae, with lobate septal 

 margins. 



2. Dibranchiata {Owen) — external shell none ; arms 8-10, 

 acetabuliferous ; epipodia united to form a funnel ; epidermis 

 with chromatophores ; an ink-bag, and two gills with branchial 

 heart at base, also exist. About 212 species are living, 139 

 being extinct. They are divided into two sub-orders : — i. De- 

 capoda {Leach) — with two tentacular arms, except in Cheiro- 

 teuthis, retractile into pouches under the eyes, and pedicellate 

 suckers. Here are included two series : — I. Chalcophora — 

 ■with an inner calcareous shell. This includes the following 

 families : — Spirulidae — shell an open spiral, camerated, sipho- 

 nate, nacreous, included in the hinder part of the body ; eye 

 with a closed cornea. Belemnitidae — extinct, with a straight 

 included, camerated, siphonate shell ; arms with six rows of 

 small suckers. Sepiadas — oval, with long, lateral fins ; eyes 

 with closed corneas ; shell prolonged to a point ; its lamellae 

 not separated by siphonate chambers (Cuttlefishes). Series 

 II. Chondrophora — shell of conchiolin supported either by 

 two internal fleshy bands (Cranchiadae, Loligopsidae), or by 

 three internal cartilages (Cheiroteuthidae, Onychoteuthidae, 

 Loliginidae). Herein are contained two groups : — i. Myop- 

 sidae — eyes with closed cornea ; littoral, including the families 

 Loliginidae — elongate, with suckers on the buccal membrane, 

 and inner shell as long as the body ; mantle free. Sepiolidae — 

 short, with rounded fins, and no buccal suckers ; mantle at- 

 tached anteriorly ; shell half as long as the back. Group 

 2. Oigopsidae — eyes with open corneae, pelagic; including 

 Cranchiadae — round, with terminal fins ; mantle united to the 

 small head by a neck band ; eyes large, and the corneal 

 opening small ; funnel with a valve. Loligopsidae — soft, 

 transparent, long, pointed behind, with terminal fins ; funnel 

 long, with no valve ; eyes stalked ; shell lancet-shaped, as 

 long as the back. Cheiroteuthidae — long, with two dorsally 



