CLASS CEPHALOPODA 



Here are placed the octopods, 

 nautili, cuttlefish, Splrula, and other 

 highly organized forms. Structurally 

 these are similar to other mollusks but 

 their mode of living is entirely differ- 

 ent. Many of them are active swimmers, 

 swift in motion, contrasting with the rel- 

 atively slow clam and inall. 



The common squid (Loligo pealii) 

 remains in deep water during the winter 

 but about May 1st enters shallow water in 

 order to lay its eggs. 



The orders under the Cephalopoda 

 are arranged with respect to the number of 

 gills together with other internal organs 

 and also the character of the shell. 



SUBCLASS DIBRANCHIATA 

 ORDER DECAPODA 

 Family Spirulidae 



Animal with elongate tentacular 

 arms; cups numerous, evenly spaced, in six 

 series and very small; body sometimes pro- 

 vided with a thickened belt and a small 

 fleshy fin on each side; eyes covered with 

 skin, lower eyelid present. 



Shell internal, of shelly nature, 

 spiral, chambered, the chambers provided 

 with a siphon, the last of sufficient 

 size to contain a very small portion of 

 the animal. See Fig. 53. 



GENUS SPIRULA Lamarck 1799 

 (SPIRAL SHELLS) 



Whorls of shell separated from 

 each other; septa or plug outwardly con- 

 cave, provided with a funnel-shaped siphon 

 on inner or curved side and reaching into 

 each cell without these directly communi- 

 cating with each other. 



SPIRULA SPIRULA Linnl. The only known 

 species of the genus. It lives in the 

 open sea. The shell Is white and pearly; 



Fig. 53 



Splrula splrula. 



Showing position 



of internal 



shell 



the two to three revolu- 

 tions not making contact. 

 Breadth 1 inch. 



This interesting 

 shell, much resembling a 

 ram's horn, is common upon 

 southern beaches. 



PI. 28, Fig. 6 

 Nantucket and Cape 

 Cod, Massachusetts 

 southward to the 

 tropics 



SPIRULA SPIRULA LINNE 



Charles W. Johnson, 

 late editor of "The Nau- 

 tilus" after hearing a pa- 

 per read by J. Henry Blake 

 at a meeting of the Boston 

 Malacological Club com- 

 posed the following lines 

 which admirably describe 

 the history and habits of 

 Splrula. 



"The chambered shells of the Splrula 



As they float upon the sea. 

 Are cast on a thousand beaches 



For any one to see; 

 But the animal that made this shell 



Was long a mystery. 



Linne called it Nautilus splrula 

 Which was not a very bad guess. 



Lamarck called it Splrula peroni 

 Crhough he'd first named it fragilis); 



And thus quite early was started 

 A nomenclatorial mess. 



Some said with that disk-like sucker 

 Attached it must surely grow. 



While the rudimentary fins would prove 

 As a swimmer it must have been slow; 



Then the chromatophores would indicate 

 That it lived in the mudi; you know. 



148 



