CAVOLINIIDAE 273 



rudimentary gill. The gill is absent in Diacria, Cleodora, Cuvierina, Limacina, and 

 Cymbulia, but is well specialized in the genus Peraclis. 



The shell in all Eupteropods is very fragile and more or less transparent. In the 

 Cavoliniidae it is symmetrical and not coiled. The upper side has fine longitudinal ribs: 

 the lower side is much swollen and striated transversely. The digestive apparatus 

 (throughout the group) consists of a long tube with buccal bulb and salivary glands, and 

 a swollen gizzard, containing four large corneous, hyaline plates and one small one. 

 These plates are so large and many-angled that their outline shows clearly through the 

 brown skin and the numerous transverse muscle bands. There are also a number of 

 small chitinous pieces. The intestine has a small caecum. The liver pancreas is not 

 attached to the stomach, as in the Gymnosomata. The genital gland adheres closely 

 to the posterior part of the liver pancreas. It varies in shape so as to fit the space 

 allotted to it by the shell, being conical in Creseis and round in Cavolinia. The 

 hermaphrodite genital duct is always very long. The jaws are always placed ventrally 

 and are not much developed. The radula is three-toothed, except in Peraclis, where 

 there is an extra, but very rudimentary, lateral tooth on each side of the series of three 

 [(i)i-i-i(i)]. 



The nervous system includes two cerebral ganglia united below the oesophagus by a 

 long commissure, two pedal ganglia and from one to five visceral centres. There are no 

 pleural ganglia. The otocysts are attached to the cerebral ganglia between these and the 

 visceral mass. The olfactory organ (Osphradium, Spengel's organ) is placed close to the 

 otocysts. Eyes are completely absent. Bonnevie (1913, p. 52), however, has suggested 

 that the curious white plates which are so conspicuous on the top of the tentacles in 

 Cleodora falcata , Pfefli'er, and Limacina heUcoides, Jeff., may be organs of light produc- 

 tion or light perception. Vayssiere (1915, p. 190) says: "J'ai pu confirmer I'absence 

 absolue des organes visuels chez tous ces mollusques, il n'y en a pas meme de tres rudi- 

 mentaires comme cela s 'observe chez d'autres Tectibranchs tels que les Philinides et 

 les Scaphander.'" 



The large pallial cavity contains the organ of Bojanus, or paired kidney, the heart, 

 and also the gills, where these are developed. 



All Eupteropods are phosphorescent. The food is wafted to the mouth by the cilia 

 and consists chiefly of Diatoms, Radiolaria and Foraminifera and occasionally of the 

 larvae of Copepods and other small Crustacea or even very young Eupteropods. 



Family CAVOLINIIDAE 



Genus Cavolinia, Gioeni, 1783 

 Cavolinia longirostris (Lesueur), 1821. 



Hyalaea longirostris, Lesueur (after Blainville), 1S21. 



Hyalaea limbata, d'Orb., 1836. 

 Hyalaea angulata, Souleyet, 1852. 

 Hyalaea fissirostris, Benson, 1861. 



