76 JOURNAL OF THE NEW JERSEY 



Any determination by a Key necessarily forces the student to 

 make a deeper investigation of parts than does any other 

 method. As a general thing, too, such investigation is made by 

 the student while the animal is still living, and the mere fact of 

 its being alive adds greater zest and interest to his work. As far 

 as I know all works yet published upon the shells of the region 

 depend almost if not entirely upon engravings of all the species 

 for their determination; and those acquainted with shells have be- 

 come so either by means of these engravings, by seeing the shells 

 in collections, or by pestering and questioning those who know 

 more than they do. This tends to make students mere shell 

 collectors, who are entirely satisfied if only they can call their 

 specimens by name. 



In writing this paper, my hope has been to interest our shore 

 dwellers and shore visitors in the habits and lifp history of our 

 shell fish. The only originality claimed for the work is the Key. 

 The classification, except of the Sea Slugs and Squids, is that of 

 Wm. H. Dall, A. M., Curator Department of Mollusks, U. S. 

 National Museum, in Bulletin No. 37. The descriptions were 

 taken and adapted from all the sources at my command. 



Deep sea and pelagic forms are excluded, except those whose 

 shells are occasionally thrown upon the beach after storms. 



This is only a preliminary manual and of necessity must con- 

 tain numerous errors that will be gladly corrected by the author 

 if brought to his attention. 



All the measurements given in the Keys and the descriptions 

 are in millimeters (25 to an inch). At the end of the descrip- 

 tions L. stands for length, H. for height, W. for width, D. for 

 diameter, An. for angle, Ap. for aperture and U. for umbo. The 

 fraction after Ap. gives the relative length of the aperture. 

 Thus Ap. J indicates that the aperture is one third the length 

 of the shell. The fraction after U. states the position of the 

 umbo. Thus U. J indicates that the distance of the umbo from 

 the anterior end is one-fourth the whole length of the shell. The 

 application of these terms to bivalve shells is shown on Plate II., 

 to univalve shells on Plate III. Plate IV. contains a protractor 

 and millimeter measurements in a convenient form for use with 

 shells. Apply the shell directly to the plate and the length, 

 width, position of umbo, angle of spire, etc., can be seen. 



