of Gasteropodous Molkisca. 415 



The auditory capsule contains a single spherical otolithe, and 

 is attached to the central ganglion at the root of the optic nerve. 



In Acteonia corrugata the auditory capsule is also furnished 

 with a single otolithe. 



EXPLANATION OF PLATES XIX. and XX. 

 Plate XIX. 



Fig. 1. Cenia Cocksii, much enlarged. 



— 2. Acteonia corrugata. 



— 3. Side view of the head of the same. 



— 4, 5, 6. Different views of Limapontia nigra. 



— 7. Spawn of the same magnified. 



— 8. Larva of the same. 



— 9. A portion of one of the lateral hepatic trunks of Cenia Cocksii, show- 



ing its granular appearance. 



— 10. A few of the granules more highly magnified, exhibiting their mi- 



nute structure. 



Plate XX. 



Fig. 1. General view of the digestive system of Limapontia nigra : a, buccal 

 mass; h, tongue; c, prehensile collar in advance of the same; 

 d, salivary gland; e, oesophagus; /, stomach; gg gg, lateral he- 

 patic tnmks ; h, intestine ; i, anus ; j, cerebral ganglions. 



— 2. Tongue removed from the buccal mass : a, prehensile collar. 



— 3. Two joints or plates of the tongue more highly magnified. 



— 4. General view of the reproductive system : a, penis ; h, crystalline 



point of the same ; a, tube of the penis ; d d, testis ; e, duct of the 

 same ; /, junction of the duct of the testis with the bulb of the 

 copulatory channel ; g, junction of the duct of the testis with the 

 tube of the penis ; hh h, ovigerous sacs containing ova ; i, dilated 

 portion of the oviduct ; j, junction of the oviduct with the tube of 

 the penis ; k^ mucous gland ; /, external orifice leading to the same, 

 and through which the eggs pass ; m, two elongated glands pro- 

 bably connected with the mucous gland ; n, shallow pouch at the 

 external orifice leading to the spermatheca ; o, copulatory channel ; 

 p, bulb of the same ; q, spern)atheca ; r, duct of the same. 



— 5. Intromittent organ of Limapontia nigra: a, penis; b, crystalline 



point ; c, tube. 



— 6. Crystalline point (much magnified) of the penis of Cenia Cocksii, 



exhibiting the perforation at the extremity a. 



— 7. Profile view of the heart of Limapontia nigra : a, ventricle ; 6, au- 



ricle ; c, aorta ; d, venous trunk leading to the auricle ; e, dorsal 

 skin ; //, clear space, probably showing the limits of a pericar- 

 dium. 



— 8. Cerebral ganglions of L. nigra, with nerves : a a, central ganglions ; 



b, commissure uniting the same above the oesophagus ; c c, lateral 

 ganglia ; d, buccal ganglia ; e Cy eyes ; //, auditory capsules. 



— 9. Auditory capsule, with otolithe, more highly magnified. 



— 10. Eye greatly magnified, exhibiting the nerve, pigment cup, lens, 



cornea, and general capsule. 



