THE RECENT AND FOSSIL MOLLUSKS OF THE GENUS 

 DISASTOMA FROM THE WEST COAST OF AMERICA. 



By Paul Bartsch. 



Assistant Curator, Division of Mollushs, U. S. National MuLseum. 



Of this genus only a single species has been reported from the west 

 coast of America, Bittium fastigiatum Carpenter. This was tersely 

 diagnosed by Dr. P. P. Carpenter in his report on the Mollusks of the 

 West Coast of America, made to the British Association for the Advance- 

 ment of Science in 1863, and published in their report on page 655 in 

 1864. Later, in 1865, it was more fully described in the Annals and 

 Magazine of Natural History, page 181. This species was collected 

 by Col. E. Jewett in the Lower Pleistocene deposits at Santa Barbara, 

 California. 



To this I now add three additional species, Diastoma chrysalloidea 

 Bartsch, from the Gulf of California; Diastoma oldroydx Bartsch, from 

 San Pedro, California, and Diastoma stearnsi Bartsch, from San Diego, 

 California.'* 



DIASTOMA FASTIGIATA Carpenter. 



Bittium fastigiatum Carpenter, Rep. Brit. Ass. Adv. Sci. for 1863, 1864, p. 655; 

 Ann. Mag. Nat. Hist., eer. 3, vol. 15, 1865, p. 181. 



Shell elongate-conic, yellowish white. Nuclear whorls two, well 

 rounded, smooth. Post-nuclear whorls flattened, much wider at the 

 periphery than at the summit, overhanging, ornamented on the first 

 seven whorls by four equal and equally spaced spiral cords, of wliich 

 the posterior is at the summit and the anterior at some little distance 



a In the preparation of the present diagnoses the following terminology is used : 

 "Axial sculpture," the markings which extend from the summit of the whorls toward 

 the umbilicus. 

 The axial sculpture may be — 



"Vertical," when the markings are in general parallelism with the axis of the shell. 

 "Protractive," when the markings slant forward from the preceding suture. 

 "Retractive," when the markings slant backward from the suture. 

 "Spiral sculpture," the markings following the directions of the coils of the whorls. 



Proceedings U. S. National Museum, Vol. 39— No. 1802. 



581 



