410 BULLETIN OF THE 



cient. Acmcea elegans Philippi (La Guayra) is a synonym of yl . Candeana, 

 as I believe from the literature P. confusa of Guilding is intended to be. 



The melanosticta above referred to, whatever be its proper name, is appar- 

 ently an excellent species, and quite distinct from A. Candeana. Orbigny 

 says that A. melanoleuca is a true Patella, but this does not agree with the 

 only specimen I have seen, and the other species he describes as Patella are 

 certaiidy Acmoeas. 



The comparatively small number of littoral species, compared with the mul- 

 titude of forms on the Pacific coast, affords a notable discrepancy between the 

 faunae of the two regions. 



The deep-water Docoglossa are few in number and peculiar. An account of 

 most of them was published by me in the Proceedings of the U. S. National 

 Museum for 1881, page 407. The progress of science during the last six years 

 has enabled me to clear up several disputed points. The result is, that the 

 genus Scutellina, long supposed to belong in this group, is (as will be seen 

 elsewhere in this paper) definitely relegated to another suborder, while Propi- 

 Udium has been proved to belong to the Docoglossa, a relation which had been 

 strongly questioned. The character and number of the gills in Propilidium 

 still remain in doubt. I suspect it has a single gill, like Acmcea, and that an 

 elongated anal papilla has been taken for another or second gill. 



In this connection, it may be observed that on several occasions in the last 

 year or two the question of the position of the osphradia in Acmcea has been 

 raised, and the importance of this item in classification has been highl}'- rated by 

 certain naturalists. Now I doubt extremely the value of the transcendental 

 theories based on the osphradia and their position, with which we have been 

 regaled at times. Nevertheless, for the comfort of those who do believe in 

 them, and as one more fact to be added to the general stock, I will describe the 

 position and character of the osphradia in Acmcea. These organs in the large 

 limpets of the western coast of America are generally orange- colored, usually 

 quite small, elongate oval, and little raised. They are often abortive or nearly 

 so. When well developed, in most species (e. g. Acmcea patina and A . spectrum) 

 they are smooth and polished, very little elevated, and have a glandular aspect 

 and unbroken contour. In others (as Ancistromesus mexicanus) the surface 

 is cellular or transversely corrugated like an abortive miniature gill, and even 

 appears as if it were porous. The}'- lose color and contract strongly in alcohol, 

 and, unless one knows exactly where to look, he will not find them in an old- 

 fashioned badly contracted alcoholic specimen. They are situated one on each 

 side of the back of the neck as it were, or, more precisely, on the transverse 

 portion of the integument above the head, and in front of the main pericardial 

 chamber, in the angle formed by the neck and the inferior surface of the 

 mantle over the head. They are not especially related to the Acmsean gill 

 either in position or development. I may add, that I described them and their 

 position about thirteen years ago;* but, as the state of science then was, in 



* Proc. Acad. Nat. Sci. Pliila. for 1876, pp. 239, 240. 



