Annual Report.] 10 [May 5, 



tended to illustrate all the genera of each family in this 

 manner. The models are made in the ordinary way of con- 

 structing plastic models. The animal is first built up in clay 

 from drawings, and then transferred to plaster by means of a 

 gelatine mould. It has been found most satisfactory to work 

 the model up only roughly in the clay, and finish all the 

 details in the plaster cast. In many cases it has been possi- 

 ble to imitate the appearance of the surface of the body of 

 the animal by covering the plaster with a thin coating of 

 wax before putting on the paint. 



For representing the animal of the Naticidae, one of the 

 more common New England forms, Lunatia heros was 

 chosen. The animal is represented crawling on the sand, 

 with the operculum lobe covering about half the shell, and 

 with the mentum thrown up well in front. The body is 

 shown as if much distended with water so as to have a length 

 equal to about three times that of the shell. 



Of the models of Lamellibranchs made, those forms pos- 

 sessing open mantles are represented as lying on the side 

 with one valve imbedded in the sand, and with the siphons, 

 foot and mantle lobes quite fully extended. Of those with 

 closed mantles some lie on the side, but others are inclined 

 backward, so as to show a portion of both valves. In 

 some groups, as the Corbulidas, where no large shells exist, 

 no attempt has yet been made to model the animal. Each 

 model is placed in the case with the family in which it be- 

 longs, and, where possible, New England forms have been 

 chosen for modelling. 



The families of Lamellibranchs represented by models, are 

 as follows : — Pholadidaa by Dactylina dactylus, of natu- 

 ral size ; Teredinidae by Teredo navalis, enlarged over four 

 times, and represented as if lying in its burrow in a section 

 of wood ; Solenidae by JEnsatella americana, the American 

 razor shell ; Myadae by My a are?iaria, the common clam of 

 New England, with the united siphons extended one and 

 one-half times the length of the shell ; Mactridaa by Mactra 



