THE RECENT AND FOSSIL MOLLUSKS OF THE GENUS 

 RISSOINA FROM THE WEST COAST OF A^IERICA. 



By Paul Bartsch, 



Curator, Division of Marine Invertebrates, United States National Museum. 



INTEODUCTION. 



It is interesting to note that the first species recorded from West 

 American waters served also as the type of the world-wide cUstrib- 

 uted genus now under discussion. The noted traveler and naturalist, 

 Chevalier Alcide D'Orbigny, in his Voyage dans L'Amerique Meri- 

 dionale, which extended over the years 1826-1833, collected a won- 

 derful lot of material and among other things a Rissoid, on the 

 coasts of Bolivia and Peru, for which he erected the genus Rissoina ^ 

 and which he christened Rissoina inca} 



Ten years later Dr. Karl Theodor Menke, in a paper, Conchylien 

 von Mazatlan mit kritischen Anmerkungen, based on a large collec- 

 tion made in part by Heinrich Melcher, of Bremen, who spent several 

 years at Mazatlan, and partly by an unnamed collector from whom 

 Doctor Menke purchased a box of shells, also from Mazatlan, de- 

 scribed Rissoa stricta ^ horn, that place. This is a true Rissoina. 



Two years after tliis, Dr. F. H. Troschel, in liis Verzeichniss der 

 durch Herrn Dr. v. Tschudi in Peru gesammelten Conchylien, de- 

 scribed Rissoina sidcifera ^ from Peru. Tliis mollusk is not congeneric 

 with Rissoina but must be referred to the Rissoid genus Iravidia of 

 Blanford. 



The same year Prof. C. B. Adams, of Amherst College, Massachu- 

 setts, published liis Catalogue of Shells Collected at Panama.* In 

 this paper, which details the result of one of the most wonderful 

 records of intensive collecting, we learn that during the period be- 

 tween November 25, 1850, and January 3, 1851 — that is, 40 days — 

 Professor Adams collected and kept data upon no less than 41,830 

 specimens of mollusks. It is equally interesting to note that al- 

 though the cases containing the specimens did not arrive until 



1 Voyage Amer. Merid., p. 395, 1840, pi. 53, figs. 11-16. 



2 Zeitschr. Malak., vol. 7, 1850, pp. 177-178. 



3 Wieg. Archiv. Naturg., vol. 1, 1852, pp. 151-155. 



< Aiui. Lye. Nat. Hist. N. Y., vol. 5, 1852, pp. 229-549. 



Proceedings U. S. National Museum, Vol. 49— No. 2094. 

 81022°— Proc.N.M. vol.49— 15 3 33 



