Introduction to Animal Morphology. 325 



gills four; tentacles numerous; ink-bag none; epipodial lamellae 

 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 Ammonitidee, 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, 159 

 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. Belemnitidoe extinct, with a straight 

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

 small suckers. Sepiadas oval, with long, lateral fins ; e 

 with closed corneae ; 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, Loligopsida;), or by 

 three internal cartilages (Cheiroteuthidae, Onychoteuthidae, 

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

 . ith closed cornea ; littoral, including the families 



iginidce elongate, with suckers on the buccal membrane, 

 and inner shell as long as the body ; mantle free. Sepiolidx- 



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



riorly; shell half as long as the back, (in.ii]> 



2. ()\(>}i*\(\ \\ith open eurne;i-, jirla^ic ; including 



-round, with terminal fins ; mantle united to the 



. an<l the eurneal 



all ; funnel with a valve, l.oli-opsuhf soft, 



tra: ; In-hind, with terminal fins; funnel 



:th no v.. ;!kcd ; shell lain el-shapcd, as 



... rhcirotc-ulhidLC long, with two dorsally 



