PTEROPODA. 207 



FAMILY II. 



Shell minute, spiral, sometimes operculate. 



Animal with fins attached to the sides of the mouth, and united ventrally 

 by an operculigerous lobe ; mantle-cavity opening dorsally ; excretory orifices 

 on the right side. 



The shells of the true limacimda are sinistral, by which they may be 

 known from the fry of Atlanta, Carinaria, and most other Gasteropods. 



LIMACINA, Cuvier. 



Etym, Limacina, snail-like. Syn. Spiratella, Bl. 

 Ex. L. antarctica (drawn by Dr. Joseph Hooker), PL XIV. fig. 41. 

 Shell sub-globose, sinistrally spiral, umbilicated; whirls transversely 

 striated ; umbilicus margined ; no operculum. 



Animal with expanded fins, notched on their ventral margins ; operc. lobe 

 divided; lingual teeth 1.1.1. 



Distr, 2 sp. Arctic and Antarctic Seas ; gregarious. 



SPIRIALIS, Eydoux and Souleyet. 



Ex. S. bulimoides, PL XIV. fig. 42. Syn. Heterofusus, Mem. 

 Heliconoides, D'Orb. Peracle, Forbes. Scaea, Ph. 



Shell minute, hyaline, sinistrally spiral, globose or turrited, smooth or 

 reticulated ; operculum thin, glassy, semilunar, slightly spiral, with a central 

 muscular scar. 



Animal with narrow, simple fins, united by a simple, transverse operculi- 

 gerous lobe ; mouth central, with prominent lips. 



Distr. 12 sp. Greenland and Norway to C. Horn, Indian Ocean, Pacific. 



? CHELETROPIS, Forbes. 



Etym. Chele, a claw, tropis, a keel. Syn. Sinusigera, D'Orb. 



Type, C. Huxleyi, PL XIV. fig. 43. 



Shell dextrally spiral, imperforate, double-keeled; nucleus sinistral; 

 aperture channelled in front; peristome thickened, reflected, with two clavv- 

 like lobes. 



Animal pteropodous ? gregarious in the open sea. 



Distr. 2 sp. S. America, S. E. Australia. 



Another minute spiral shell, recently discovered, may be noticed here : 



MACGILLIVRAYIA. Forbes. 



Named after its discoverer, the Naturalist to H. M. S. Rattlesnake. 

 Type, M. pelagica, PL XIV. fig. 44. 



Shell minute, dextrally spiral, globular, imperforate, thin, horny, trans- 

 lucent ; spire obtuse ; aperture oblong, entire ; peristome thin, incomplete, 

 operc. thin horny, concentric, nucleus sub-external. 



JL 



