OF MOLLUSCA. 89 



Littorina littorea, L. retusa, L. petrcea, and several others, are 

 oviparous ; the egg-masses of L. retusa are oval, almost three 

 lines broad. Some species, as L. rudis and L. rugosa, are viviparous, 

 the upper part of the body in the cavity of the shell being filled with 

 living young at the end of summer. 



The colour of the common English L. retusa agrees with the 

 colour of the shell ; thus the orange animals have orange shells, the 

 dusky ones dusky shells. Other species, as L. vulgaris, appear to be 

 more permanent in their colour ; its animal is always varied with 

 black lines. 



Mr. W. Thompson obtained at Weymouth several examples of 

 Littorina rudis in copulation with L. littoralis (Nerita /.) ; in every 

 instance L. rudis was the male. He remarks, " From these instances, 

 I infer L. palliata to be the hybrid progeny of L. rudis and a female 

 L. littoralis. The only doubt in my mind as to this inference is, that 

 I have not as yet found any specimens of L. palliata on this coast ; 

 but neither have I found any other shell that might in any way be 

 considered as the produce of L. rudis and L. littoralis. I found in 

 all eight couples : the probability of some being unfruitful, and the 

 further probability of the hybrids not being prolific, will, I think, 

 form just grounds for the rarity of the species." — Ann. fy Mag. Nat. 

 Hist. 1852, ii. 76. 



Littorina peruviana is abundant in the anfractuosities of rocks 

 so high above the highest water mark, that they can be only wetted 

 by the spray during tempests ; if placed in sea water, they develope 

 themselves and quickly search for means of escaping from it and reach 

 some dry place. L. araucana lives on rocks near the high water 

 line, and L. umbilicata is numerous in Peru near the low water 

 mark. — D' Orbigny. 



3. LlTHOGLYPHUS. 



Eyes basal. Shell ovate, solid, covered with a brown periostraca ; 

 mouth ovate ; lips thick. Operculum ovate. — Adams, Gen. Moll. 

 t. 35. f. 1 a. Fluviatile. 



1. L. piscium, t. 124. f. 5. 



2. L. Lapidum, t. 124. f. 4. 



The snout of Lithoglyphus Lapidum and L. piscium is rather pro- 

 duced in front, as far or farther than the edge of the foot, annulated 

 above. The tentacles are subulate, with the eyes on a slight promi- 

 nence at the hinder outer side of their base. Operculum horny. 



Lithoglyphus piscium lives on stones in the little marshes of the 

 river La Plata, and affords food to the Bagri or Siluri. Lithoglyphus 

 peristomatus lives in deep water in the river Parana attached to 

 stones ; they live in large families, each shell supporting the oval 

 eggs. They are only to be procured when the river is low. 



Dr. Philippi has placed Lithoglyphus and Hydrobia with spiral 

 opercula as subgenera of Paludina, and Paludomus with an annular 

 operculum as a subgenus of Melania. — Handb. der Conch. 167, 168, 

 1853. 



