' THE NAUTILUS. 



dimensions, though the mass of the animal in Pcmopea and Tresus is 

 probably greater than in our species. On the other hand, among 

 the Prionodonts, such as Inoceramiis, etc., a number of fossil forms 

 occur which were larger; and the spread of the valves of the recent 

 pearl oyster, Meleagrina, sometimes exceeds a foot, when closed. 



In a recent examination of all the generic forms supposed to 

 belong to the family Lucinidce, I have been led to the conclusion 

 that there is no evidence that the Palaeozoic fossils referred to 

 Paracyclas Hall, should be, placed in this group. They appear to 

 be absolutely without any of the characters which are diagnostic of 

 Pelecypods belonging to the Lucinidce. 



I may add that the Clairemont limestones contain two other 

 species of this family, one a true Lucina of the type of L. edentula 

 Reeve, and the other a species of Phacoides belonging to the sub- 

 genus Lucinoma Ball., typified by L. Jilosa Stimpson ; a group 

 which has a remarkably wide distribution in age, space and depth of 

 water. 



THE AMERICA PHYSJE. 



BY O. A. CRANDALL, SEDALIA, MO. 



Physa anclllaria Say. 



Including the subspecies Pliysa vinosa Gould, magnalacustris Wal- 

 ker, and crassa Walker. 



This species was described in 1826 from forms taken from the 

 Delaware river near Easton, Pa. Typical forms are still found in 

 the same locality. It differs from P. heterostropha Say, in its larger 

 size, more inflated form and by its coarser lines of 'growth. The 

 greatest difference lies in the. manner in which the whorls are put 

 together, and the resulting change in the structure of the suture and 

 form of the spire. In that species the whorls lie against each other, 

 forming a more or less impressed suture, while in this form the 

 whorls overlap in such a manner as to make the suture appear as a 

 mere line. The type is shouldered, but in a majority of specimens 

 the shoulder is not prominent. It has a little more than four 

 whorls, the last very large, and the columella is always twisted. It 

 is an annuan, but forms are found having two varicose lines on the 

 last whorl near the margin. 



