n'EROPODS. 



229 



II YALE A GIBHOSA. 



Division a. THECOSOMATA. Animals provided with an External Shell. 



1. Family HYALEID.K : Genera Jfi/nlea ; Cleodora ; Orescis ; Cuvieria ; Etirybia ; Cymbulia ; Tiedemannia. 



2. Family LIMACINIUJE : Genera Limacina ; Spirialis ; Cheletropis; MacgMivrayia. 



Division b. GYMNOSOMATA. Without a Shell. 

 3 Family CLIIDJE : Genera Clio; Ptu'iiinodermon ; Pelagia ; Cymodocea. 



Professor Sir Wy ville Thomson, in his " Voyage of the C/taflenger," writes : " When dredging 

 off Portugal, at depths beyond five hundred fathoms, in the now well-known 

 ' Globigerina Ooze,' that is to say, a greyish calcareous paste, soft on the surface, 

 becoming tinner below, and made up in a great degree of the shells of forami- 

 nifera, chiefly of the genera Globigerina and Orbulina, entire or more or less 

 broken up and disintegrated, along with the foraminiferous shells some other 

 shells of much larger size enter, in varying proportions, into the composition 

 of the ooze, or perhaps may be rather said to be mixed with it. These are 

 principally shells of Pteropods, with a few of those of Heteropods and of 



pelagic Gasteropoda. " Most of these animals live on the bottom of the sea, as their 



organisation demands. One or two only of the shell-making genera are pelagic." 



Of the genus Clio we " have in the Northern Polar Seas the Clio horealis, which is there found 

 in such plenty as to constitute a considerable portion of the Greenland Whale's food. Passing over 



the intermediate oceans, that genus is, according to S. P. Woodward, 

 represented in the Antarctic Ocean by some few species, but, according to 

 H. and A. Adams, by only one, the Clio australits. 



" The Pteropoda are farther removed than the Heteropoda are from 

 the typical Gasteropoda, and are much simpler in their structure. The 

 head is not so markedly separated from the body, and the organs of 

 sense are rudimentary. The body is conical and sometimes spiral, and 

 is very usually contained in a delicate shell, sometimes spiral in form, 

 more frequently conical or tubular, or like an ornamental flower-glass, 



or like a watch-pocket. The foot is modified into two wing-like appendages, one on either side of the 

 mouth. These are frequently brightly coloured when the animal is living, and different parts of the 

 body show iridescent blues and greens. Multitudes of these little things may now and then be seen 

 on the surface of the water, fluttering with their wings and glittering in the sunshine, to be compared 

 with nothing more aptly than with a congregation of the more dressy of 

 the Bombyx Moths, as one sometimes comes upon them on a sunny morning, 

 just after a family of them have escaped from their chrysalises. 



" The Pteropods are much smaller than the larger forms among the 

 Heteropods ; the largest of the present day are 

 not more than about an inch in length, though 

 antediluvian species of the genus Conularia and 

 its allies sometimes reach a length of nearly two 

 feet. They make up for their 

 small size, however, by their 

 numbers. Everywhere in the 

 high seas they absolutely 

 swarm. They are not always 

 to be taken in the towing-net, 

 as they seem to have a habit 

 in the heat of the day, and 

 when there is any wind, of 



swimming a little way below the surface, but in a fine calm evening, no matter where, a haul of 

 the towing-net can scarcely be made without catching many of them. 



" The most widely distributed species in the Atlantic seems to be Diacria trispinosa, with a little 

 pocket-like shell of some weight and strength, shaded purple and white. Several species of Cavolina are 



HYALEA LONGIROSTKIS. 



CI.EODORA CUSPIDATA. 



C. LANCEOLATA. 



C. COMPRESSA. 



