OF PLANORBIS AT STEINHEIM. 31 



or even a majority of thera, which may have been caused by the physical pectiliarities of 

 the environment, and which can be attributed solely to their action. 



The tendency to increase the spirality in each series at first sight appears to be a 

 uniform result which might be attributable to the habitat alone. But, as has been shown, 

 this is a general tendency expressed without regard to locality ia nearly all series of the 

 MoUusca, and shows very forcibly what the author means by the tendency of growth- 

 force to reproduce under the most diverse circumstances similar forms in similar 

 succession. 



The well-known researches of Mr. J. A. Allen ^ and other American naturalists among 

 birds and mammals have shown that such general modification in the colors, bUls, tail and 

 wing feathers of birds, and in the pelage and size of ears and feet in mammals, do take 

 place in given localities, and are attributable probably to certain well defined local causes, 

 such as humidity, temperature, etc. My own similar results obtained from the commercial 

 forms of the keratose sponges,^ and Mr. Scudder's ^ in the insects, also seem to show that 

 there are such general effects on the organization which may be separated from other 

 categories of characteristics. 



There is not the slightest reason for regarding any of the series, as purely scalariform 

 and distorted, except the first and second sub-series. These also agree in form with the 

 Planorbis found in the famous locality of Magnon, where the environment is evidently 

 unfavorable to the race. 



To these instances I can happily add another of peculiar interest which occurs in a marl 

 bed at Lawlor's Lake, near St. John, New Brunswick. My attention was first called to 

 this locality by the kindness of Prof. E. S. Morse, who sent me a lot of shells collected 

 there by Prof. C. F. Hartt, late Director of the Geological Survey of Brazil, whose 

 untimely loss was regarded here, as well as in the country of his adoption, as a public 

 misfortune. 



Siuce the receipt of these I have personally surveyed the locality in company with 

 Mr. G. F. Matthews, a well known geologist of St. John, attached to the Canadian Survey. 

 Residing several weeks in the vicinity, I gathered a large collection, which is now 

 undergoing the process of sifting. The shells are all scalariform and distorted so as to 

 resemble closely in form and aspect the third sub-series and the Magnon Planorbes, but 

 they all belong to the genus Valvata (an unquestionable identification). 



It is also worthy of remark, that a true Planorbis is found abundantly side by side with 

 the distorted Valvatse, so similar to PI. levis, that I think it may prove to be identical. 

 This is also distorted but to a less degree. It would be premature to attempt to give a 

 description of the probable condition of the lake when the distortions were produced in 

 Valvata, but I hope to be able to present, in course of time, a joint memoir written by 

 Mr. Matthews and myself. It may be observed, however, that none of the distorted 

 Valvatae now exist in the lake itself, upon the banks of which, and in immediate 

 contact with the water, lie the deposits of marl containing the extinct shells. In aU 

 these instances of pure distortion, as well as in others observed by me in speci- 



1 Bulletin Mus. Comp. Zool., Vol. 2. ^ Revision of Oedipodidae, Proc. Best. Soc. Nat. Hist., 



' North American Poriferse, Mem. Bost. Soc. Nat. Hist., Vol. 17, p. 482-83. 

 Vol. 2, pt. 2, 1877. 



