DECAPODA. 25 



at least, the female, deprived of her precious burden, beats 

 herself against the sides of the vessel in which she is placed 

 and shortly dies. 



Sjyecies of Argonauta. 



Argo, Limi. (Ocythoe tubercu- hyans, Soland. (Ocythoe Cran- 



lata, Rafin.). chii, LeacK). 



gondola, Dillw. oryzata, Meusch. (Octopus rari- 



Gruneri, Dunher. cyathus, Blainv.). 



Owenii, Adams and Eeeve. 



Order DECAPODA. 



Body naked. Head separate, with ten fleshy arms, the 

 two longer arms furnished with peduncled cups with a 

 horny circle; eyes fi-ee in the orbit. Siphuncle entire; gills 

 two. Foot none. An internal medial shell. 



In this order, the two longer arms, sometimes called 

 tentacles, have expanded ends ; the eyes are moveable 

 in their sockets, and the body is always provided with 

 a pair of fins. The funnel or siphuncle, is usually pro- 

 vided with an internal valve. The decapods are con- 

 veniently divided into those with an internal horny pen 

 {ChondropTiora) ; those with a calcareous bone {Sepia- 

 phord) ; and those with an internal chambered calcareous 

 shell {Behmnopliord) . 



The long tentacular arms of the Decapodous Cephalopods 

 originate within the circle of the other arms, and are more 

 or less retractile into pouches under the eyes, except in 

 Cheiroteuthis^ where they are non-retractile. These arms 

 serve to secure their prey when beyond the reach of the ordi- 

 nary arms, and to moor the animals to floating bodies. In 

 many fossil genera, the chambered shell is combined with 

 the gladius or pen, and in some, the internal shell resembles 



VOL. I. E 



