232 AMERICAN JOURNAL 



lateral teeth variously disposed upon the area, on each side of 

 the median line. 



The following synopsis will indicate the various groups and 

 their chnraeters with special reference to the species of the 

 north-west coast of America. Witli regard to the species men- 

 tioned their synonymy, when not given, will he found at length 

 in the excellent papers of Dr. Carpenter, and the other works 

 alluded to in the foot notes. The generic synonymy, which was 

 not given in full by Dr. Carpenter, is here worked out, as far as 

 the materials at hand will allow. The absence of a number of 

 species of which the soft parts are unattainable at present, will 

 be noted by the student. These gaps are to be regretted, but 

 will doubtless be made good in time. Meanwhile, sufficient in- 

 formation has been obtained to render our knowledge of a num- 

 ber of groups moderately complete, and while it is possible that 

 the examination of the soft parts of the many species ye! unknown 

 except by the shell, may add several groups to those already 

 eliminated, still it is probable that a very large proportion will 

 fall naturally into the genera here indicated. 



The materials upon which the following approximation to an 

 arrangement of the limpets is based are as follows : For the 

 species of the north-west coast of America, upon my own rather 

 considerable collections in that quarter, and those of the Scien- 

 tific Corps of the W. U. Telegraph Expedition, under my charge; 

 comprising many thousand specimens, both in a dry and an al- 

 coholic condition, and obtained in a range extending fl'om San 

 Juan del Sud, on the west coast of Nicaragua to Bering iStrait ; 

 the large collections of the Smithsonian Institution, named by 

 Dr. P. P. Carpenter, whose knowdcdge and careful consideration 

 of the subject is excelled by none ; and specimens collected by 

 Messrs. Stearns, Cooper, Rowell, Swan and others in the same 

 collection. For the Patellidce and most of the species not from 

 the north-west coast I am indebted to Dr. Wm. Stimpson, the 

 Boston Society of Natural History, the Museum of Comparative 

 Zoology at Cambridge, Mass., and to the collections of the 

 Wilkes Exploring Expedition in the Smithsonian Cabinet, for 

 examples. In this group my alcoholic materials have been more 

 limited than among the Acmceidce, yet they have been sufficient 

 to establish the existence of several well marked groups not 

 hitherto restricted. The notes on the colors and external ap- 

 pearance of the animals when not taken from my own" notes, 

 those of Mr. Couthouy, or some other author mentioned, are 

 from the alcoholic specimens and, in some instances, perhaps 

 may describe the general appearance of a few individual speci- 

 mens rather than that of a whole race ; any erroi-s due to this 



