MUSEUM OF COMPARATIVE ZOOLOGY. 71 



Family PLEUROTOMIDCE. 



The species of this family are, as is well known, extremely numerous; and 

 of a majority, the operculum, if present, and the soft parts are unknown. A 

 thorough review of the family, recent and fossil, would be a work of some 

 years, well worth doing, Lut impossible for the writer at the present time. 

 Much has been done toward bringing together the material by Tryon, Bellardi, 

 Weinkauff, and others, while the arrangement of the subordinate groups adopted 

 by Dr. Paul Fischer in his Manual is by far the best we have. It will, practi- 

 cally, be followed here, with some trifling deviations ; but as the shells with 

 which I have to do have for the most part no traces of the soft parts, I shall 

 neglect for the time the subordinate divisions, into which a reference would be 

 a merely tentative character. As in other cases, I shall not adopt names which 

 appear in the works of authors anterior to, or who did not adopt the binominal 

 nomenclature of Linnaeus; and when a name is of reasonably euphonious con- 

 struction and Latinity of form I cannot follow those who, after many years of 

 usage, would modify it into conformity with an arbitrary standard of classical 

 purity. A self-evident misprint or an error of spelling in a proper name 

 which has not become fixed by usage may be corrected, but the essential prin- 

 ciple of nomenclature is to have a fixed name for an object, and this principle 

 should not be violated for slight cause. It is much more important that names 

 should be permanent, than that they should be elegant, of pure Latinity, or of 

 applicable meaning. 



It is highly probable that, when the eight or nine hundred species of Pleuro- 

 tomidce known from the Tertiaries of Europe are compared, a number of the 

 recent species about to be described will be found represented. But even the 

 best figures are not satisfactory for critical comparison, and the last great work 

 of Bellardi is not accessible to me; so that the final correlation of the recent 

 and fossil forms will not be attempted here, though such comparisons as are 

 practicable, especially with the Antillean Tertiary fauna, have been carefully 

 made. 



It is somewhat curious that in the until recently three most available manu- 

 als, Woodward, H. & A. Adams, and Chenu, under the head of Pleurotomidce 

 no references are made to the office or function of the " notch," and in each 

 case there is said to be a "slit" in the mantle behind. In AVoodward alone is 

 the anal or excurrent function of the posterior sinus alluded to, and by him 

 oidy in general terms, while the Pleurotomidce are not mentioned in his list of 

 examples. It is now known, that in the Fissur ell idee, the Pleurotomariidce, the 

 Pleurotomidce, and numerous other groups of Gasteropods, the anterior sinus 

 when it exists, aided by an extensile fold of the mantle (siphon), forms the 

 channel of water to the gills, while the secondary or posterior sinus serves as a 

 sluice for the ejection of water (after it has passed over the gills) and the renal 

 and intestinal excretions. In this way pollution of the inward current to the 

 gills is avoided. In very few species of Pleurotomidce is there anything which 



