1880. ] - Recent Mollusca during the year 1879. 431 
subjected to analysis, while their exotic species are usually enu- 
merated. Most of the forms are from Alaska, but several of the 
more elegant species are Californian, while a special interest 
attaches to the rediscovery at Unalashka, and identification by 
Dr. Bergh, of the singular and anciently described Tritonia tetra- 
guetra of Pallas. A number of Cooper’s ill-defined Californian 
Species are now placed on a solid basis, and several new generic 
forms are characterized. The paper does not admit of a proper 
representation by an abstract, and the reader is referred for fur- 
ther information to the original. It will be followed by a second 
part containing eight additional plates, and is based, for the most 
part, on the collections of Mr. W. H. Dall in Alaska and Califor- 
ma from 1865 to 1874. 
Another paper, in part aidia, based on the same collec- 
tions, is that of Mr. W. H. Dall in the Proceedings of the U. S. 
National Museum, a “ Report on the Limpets and Chitons of the 
Alaskan and Arctic regions, with descriptions of genera and spe- 
cies believed to be new” (l. c. pp. 281-344, Pl. 1-v, Feb. 13, 
1879). This paper contains a summary intended to exhibit all 
that is known in regard to the anatomy and development of the 
Chitonide, including the results of the author’s investigations and 
a synopsis (with some additions and rectifications) of Carpenter's 
classification of the group, in which a large number of genera are 
for the first time characterized ; and others, defined by Dr. Car- 
penter (in his table of the regular Chitons, 1873), are more fully 
alluded to. The plates represent dissections ae the radula of 
forty-five species belonging to thirty-three genera t more 
than a dozen species had previously been figured, and of these 
only a few (by Sars and Lovén) in an intelligible manner. The 
author’s observations so far as they extend agree in the main with 
those of Von Ihering, which were made about the same time at 
Trieste. The renal pore described by Ihering, but not found by 
Dall, appears from information received from the former, to have 
been due to a misconception. As the limpets had been already 
treated rather fully by the author, the list here given is merely 
a synopsis, with additions and corrections, of his previous work. 
The work so far as the region it covers has a somewhat mono- 
graphic character, and it is hoped will serve as a preliminary to 
the elaborate monograph of Dr. Carpenter, which is in process 
of preparation under the direction of the Smithsonian Institution. 
