566 bartsch: northwest coast moli^usks 



tions have as yet been published. I have therefore briefly char- 

 acterized these forms in the present paper to give a proper status 

 to these names. 



The family Caecidae is being subjected to a thorough revision 

 at the present time by the writer, and only those West American 

 forms which are listed in the above mentioned summary are con- 

 sidered here. The species belonging to the region farther south 

 will be dealt with in the fuller report. , 



Key to the Genera of the Family CAEcmAE 



Operculum conic Brochuia. 



Operculum flat or concave. 



Sculpture absent (excepting incremental lines) Farlulum. 



Sculpture not absent. 



Sculpture of raised spiral ridges only Elephantulttm.'^ 



Sculpture not of raised spiral ridges only. 



Sculpture of raised spiral ridges and axial r'mgs... Elephantanelhmt. 

 vSculpture of axial rings only. 



Axial rings strong and distantly spaced Caecum. 



Axial rings slender and closely spaced Micranelhim. 



Fartulum Carpenter, Cat. Mazatlan Shells, 525. 1856. 



Shell smooth, excepting microscopic incremental lines. Type Caecum 

 laeve C. B. Adams. 



The genus Fartulum is represented by four species in our Northwestern 

 waters, of which three are undescribed. (^f these, F. orcutH Dall is 

 the smallest and has the aperture slightly contracted. It is also some- 

 what laterally compressed, which lends the aperture an oval outline. 

 The other three species are circular in section. Of these, F. occidentale 

 is the largest. This has scarcely an indication of a lateral spur to the 

 plug, while in F. hemphilli and F. bakeri a well developed claw-like 

 spur is present. Fartulum hemphilli is always larger in equivalent 

 stages and lighter colored than F. bakeri. 



^ Since the early whorls are coiled in planorboid fashion, and the adolescent and 

 adult stages are simply portions of the solutely coiled part, it is proper to refer to 

 the sculpture that coincides with the incremental lines, that is parallels the aper- 

 ture, as axial, and that at right angles to this as the spiral. The latter, therefore, 

 coincides with the long axis of the adolescent and adult shell. This nomenclature 

 is used in conformity with that employed in all my former papers on Gastropods. 



