ZOOLOGY. 305 



Mollusks. 



In a recent lecture on the forms of passage between the 

 Annelids and Mollusks, Professor Perrier seems to adopt the 

 idea, already suggested by two or three naturalists, that the 

 Mollusks are in reality, to use Perrier's own words, " worms 

 condensed into two or three segments." Is this the begin- 

 ning of the end, and are we finally to regard the Mollusks as 

 originally descended from worm-like forms, and therefore as 

 not forming: a distinct sub-kingdom of animals? 



The anatomy of the common mussel (3Iytzlus edulis) is 

 elaborately treated by A. Sabatier in the Annates des Scien- 

 ces Naturelles. The essay fills 132 pages, and is illustrated 

 by nine folding plates. 



In an essay on the Pliocene fresh-water shells of Southern 

 Austria, by Dr. Neumayr and Herr Paul, the authors describe 

 numerous modifications of the genus Vivipara, or Paludina, 

 which occur in prodigious abundance throughout the whole 

 series of fresh-water strata. Of this genus there are forty 

 distinct forms (Dr. Neumayr very properly hesitates to call 

 them all species), which are named and described in this mon- 

 ograph, and between which, as the authors show, many con- 

 necting links, clearly illustrating the mode of derivation of 

 the newer from the older types, have been detected. The 

 authors, remarks Mr. J. W. Judd, in Nature, have demon- 

 strated that the species with highly complicated ornamenta- 

 tion were variously derived by descent the lines of which 

 are in most cases perfectly clear and obvious from the sim- 

 ple and unornamented Vivipara achatinoides of the Con- 

 oferien-Schichten, w T hich underlies the Paludina beds. Some 

 of these forms have been regarded as types of a distinct 

 genus (Tidotoma) by Sandberger. "And hence we are led 

 to the conclusion that a vast number of forms certainly ex- 

 hibiting specific distinctions, and, according to some natural- 

 ists, differences even entitled to be regarded as of generic 

 value, have all a common ancestry." 



Dr. J. W. Dawson writes to Nature that he has found at 

 the South Joggins coal-mines, in Nova Scotia, a number of 

 well-preserved shells of Pupa vetusta, the oldest of land 

 shells. It appears that this little shell is found at the bot- 

 tom and top of beds 2000 feet in thickness, including many 



