346 THE AMERICAN MONTHLY [Nov., 



d Meso-thorax separated from Meta-thorax by a 



sutnre. Trinoton 



dd Meso-thorax nnited to Meta-thorax without suture- 



Laemabofhrium 



aa No orlntal sinus or if present shallow or covered by an expansion 



of upper part of head. 



b Sides of head straight or a little concave. Forehead with two 



palettes. Phy^OHtomum 



bb The sides of the head sinuous without palettes. 



c Body very broad. Meta-thorax shorter than pro-thorax . 



Eureum* 



cc Body elongate. Prothorax shorter than meso-thorax and 



meta-thorax together. 



d Orbital sinus occupied by a strong swelling, the 



bands of the sternum forming a quadrilatera 



without median spots. Niizschia 



dd Orbital sinus without swelling, slightly Indicated 



or wanting entirely. Sternum with median 



spots. Menopon 



A A Tarsus with a single claw, (infesting guinea pig). Gyropus 



*Not yet recorded for North America. 



To Mount Certain Salts. 



By NO SIG. 



PARIS. 



DI-ACETATE OF COLDER. 



Di-acetate of copper is a very good example of a di- 

 chroic crystal. It shows a strong blue color in one 

 direction and a bright green in the other. To see this 

 effect, it is only necessary to use the polarizer, the ana- 

 lytic effect of the salt supplying the place of the analy- 

 ser. 



This salt should.be allowed to evaporate spontaneously, 

 and the slide must be thoroughly dried before the salt is 

 mounted. 



The crystals will stand the heat of the hot plate with- 

 out any danger of their being spoiled ; so that they 

 could be mounted in balsam w4tli great facility, but un- 

 fortunately when mounted in balsam, although the crys- 

 als are pretty distinct, they are surrounded with a halo 



