232 PROCEEDINGS OP THE ACADEMY OP 



Synopsis of the Genus Rangia. 



RANGIA, Desmoulins, (1832, Hermannsen). 



Clathrodon, Gray, MSS. Conrad, 1831. 



Gnathodon, Gray, 1837. 



1. Rangia cyrenoides, Desmoulins. (1831, Bronn.) 



G. cuneatus, Gray. 



2. R. flexuosa, Conrad, (Gnathodon,) 1840. 



G. rostratum, Petit de la Saussaye, 1853. 



3. R. parvum, ib. (Gnathodon.) 



4. R. men die a, Gould, (Gnathodon,) 1851. 



G. trigonum, Petit de la Sauss., 1853. 

 Fossil Species. 



1. Rangia cl athro d o nta, Conrad, (Mactra.) 



Gnathodon, Grayi, ib. 



2. R. Lecontei, Conrad, (Gnathodon.) . 



3. R. m i n o r , Conrad, (ib.) 



PLEIODON, Conrad. 



The discovery of a new species of this African genns in Lake Tanganyika 

 suggests the probability that Pleiodon will prove the predominant form of 

 Unionidae in tropical Africa, and we may anticipate the discovery of many 

 species by future explorers. It occupies in geographical distribution as impor- 

 tant a position as Castalia and Triquetra do in tropical South America. I 

 presume from the peculiar and distinct character of the hinge of Pleiodon, 

 that the animal will be found somewhat different in organization from those of 

 other genera of Unionidaj. It will be interesting to learn whether this form is 

 accompanied or not by species of the nearest allied genus Mutela, at present 

 known only to exist in the Nile. 



PARAMYA, Conrad. 



I propose the above name as a substitute for Myalina, Conrad, figured and 

 described in " Foss. of Medial Tert. of the U. S." p. 65, pi. 36, fig. 4. A very 

 different genus was designated Myalina, by De Koninck, and has priority. 



Geographical distribution of the Genus L e m o p s i s Sassi. 



Recent species. Red Sea, 1. Cape of Good Hope. 1, 120 fathoms. Singapore, 

 1. Norway, 1. 



Fossil species. Eocene of Claiborne, Alab. 7. Texas, 1. English crag. 2. 



D'Orbigny, in his Prodromus, names 7 Jurassic species, 3 Cretaceous sp., 17 

 Miocene, and 1 Subappenine sp. of European formations. In North America I 

 believe no species has been found older than those of the Eocene, and no 

 recent one. 



ADEORBIS, Wood. 



This genus occurring recent in England, California and the West Indies, and 

 fossil in the English Miocene, is represented in the Miocene of the United 

 States by 1 species. 



A. 1 y r a , (Delphinula lyra, Con.,) see Proceed. Acad. Nat. Sci. vol. 3, 

 p. 20. 



[June, 



