WEST AMERICAN PYRAMIDELLID MOLLUSKS. 7 



Two of the species above mentioned having been inadvertently 

 given names which had ah'eady been used, W. II. Dall in the Nautilus 

 for March, 1908, proposed the new names Turhonilla (Pyrgiscus) 

 castanella and Odostomia {Amaura) cavfieldi, for T. castanea and 0. 

 montereyensis . 



In 1908,° Dall describes Odostomia (Evalea) atossa from San Pedro, 

 California. 



It would have extended this review to inordinate length had we 

 attempted to refer to the instances where west American species are 

 merely alluded to in the literature. 



The drawings with which the present paper is illustrated were 

 mostly made by Miss Evelyn G. Mitchell; some of them were the 

 work of our regretted collaborator, the late Dr. J. G. McConnell. 



The temperatures of seawater cited in the text are in degrees of 

 the Fahrenheit scale. 



CLASSIFICATION. 



Family PYRAMIDELLID.^.*- 



Gastropods with the radula absent or obsolete ; the operculum ovoid 

 paucispiral, with the apex anterior, a thread-like arcuate ridge on the 

 proximal side, the inner margin notched in harmony with the plaits 

 of the pillar when prominent; foot short, moderately pointed behind, 

 with a small operculigerous lobe above and sometimes a small tentac- 

 ular appendix on each side, in front feebly auriculate or undulate; 

 mantle feebly canaliferous on the right upper margin; a single 

 branchia; verge subcylindric, elongate; head with two flattened 

 subtriangular or elongate tentacles, connate, grooved or auriform 

 in the larger forms, the funicles with a ciliated area; eyes beliind or 

 between the bases of the tentacles ; below the tentacles an oral orifice 

 from which extends a long retractile subcylindric proboscis, but 

 there is no muzzle like that of Scala; below the oral orifice is an 

 organ named by Loven the mentum, which is usually more or less 

 medially grooved or fissured, and hence, at its anterior end, more 

 or less bilobate, and extensile or retractile before or behind the 

 front margin of the foot. The shell is turrited, with a plicate axis; 



oProc. U. S. Nat. Mus., vol. 34. 



&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 

 Ihe 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. 



