76 



RANDOM NOTES ON NATURAL HISTORY. 



The Shell-Bearing Mollusca of Rhode 

 Island. 



BY HORACE F. CARPENTER. 



Chapter XXI. 



Family 44. Ampnllariidse, large globular 

 shells, living in fresh water lakes and 

 rivers, retiring into the mud during the dry 

 season. 



The species are more than one hundred 

 and fifty, divided among four genera, and 

 four sub-genera, all inhabitants of tropical 

 or semi-tropical parts of the world. A few 

 species are represented in the southern 

 parts of the United States. 



• Family 45. Truncatellidse. Animal 

 amphibious, inhabiting margins of streams, 

 salt marshes, etc. There are six genera, 

 four sub-genera, and about one hundred or 

 more species. 



Genus Truncatella, Risso. 



Of the six genera comprising the Trun- 

 catellidae, this genus alone is represented in 

 America. It is called the looping snail. 

 It progresses by contracting the space be- 

 tween the foot and the li^js like the geomet- 

 ric caterpillar. The type of the genus is 

 the Truncatella truncatula, Drap., which 

 also happens to be the one which inhabits 

 Rhode Island. There are sixt3'-two species 

 of this genus. 



64. Truncatella truncatula, Drap. 



I have never seen a description of this 

 species ; have never seen a specimen of the 

 shell ; have never heard of its being found 

 anywhere in the United States excepting at 

 Newport, R. I., and all I know about it is 

 the following quotation from A. E. Verrill's 

 Cat. Mar. Moll, p. 525, 1882 : 



" This species was found by the writer, 

 living in considerable numbers, and of all 

 ages, among the docks of Newport, R. I., 

 Jul^', 1880. It occurred among decaying 

 seaweeds thrown up at high-water mark, 

 both among tlie vegetable matter and on the 

 under side of stones. 



" Common on the coasts of Europe in 

 similar localities. Perhaps introduced on 

 this coast by shipping, but it ma^' have 

 been hitherto overlooked. It was asso- 

 ciated with Assiminea Grayana and Alexia 

 myosotis." 



Family 46. Cyclostomidae. This is an 

 immense family of operculated land shells, 

 breathing air. It is divided into five sub- 

 families, thirty-two genera, fift}' sub-genera, 

 and contains over twelve hundred species, 

 not one of which inhabits New England. 

 There is one species only in the United 

 States, which inhabits Key West, Florida, 

 but hundreds of species of these beautiful 

 terrestrial moUusks cover the numerous 

 islands of the West Indies. 



Family 47. Helicinidae. This is also a 

 large famil}' of operculated land shells. It 

 consists of nine genera, seventeen sub- 

 genera, and over five hundred species, 

 mostly confined to the West Indies. Four 

 species inhabit the United States, one in 

 Texas, one at Fort Dallas and Key Bis- 

 cayne, Florida, one near New Orleans, and 

 one from Texas to Georgia, and from Ten- 

 nessee to Florida. None are found farther 

 north. 



It was stated in Chapter V., Random 

 Notes, Vol. I., p. 9, 1884, that the sub-class 

 Prosobranchiata is divided into four orders, 

 viz. : Pectinibranchiata, Scutibranchiata, 

 Pol3^placophora, and Nucleobranchiata. 

 We have now given descriptions of all the 

 Rhode Island shells belonging to the first 

 order of the sub-class Prosobranchiata. 

 There is but little difl^erence in the animals 

 of the second order from those of the first ; 

 in fact, the description given in Chapter V., 

 of Pectinibranchiata will very closely ap- 

 pW to the Scutibranchiata. The very latest 

 authority recommends the suppression of 

 this order and its sub-orders entireh', and 

 the merging of its members in the previ- 

 ousl}'^ described Pectinibranchiata. I shall 

 therefore depart from the arrangement 

 originally intended (in regard to this sub- 

 class onl}'), and drop the name of Scutibran- 

 chiata, and proceed to enumerate its families 

 and genera as though a continuation of the 

 Pectinibranchiata. 



Family 48. Neritidse : four genera, 

 seventeen sub-genera, and over three hun- 

 dred and seventy species, all foreign to our 

 fauna. 



Family 49. Liotiidae : two genera, 

 nine sub-genera, and twent3^-five species ; 

 also foreign. 



Family 50. Rotellidae : two recent and 

 eight fossil genera, with twenty-eight re- 

 cent species, all foreign. 



