8 U.S. NATIONAL MUSEUM BULLETIN 259 



at each examination of losing one or more critical structures. A 

 second disadvantage is that of limited clearing of the material to be 

 observed. The second method, which involves making permanent 

 slide mounts of appendages, is in my opinion the superior of the two 

 methods and was the one adopted for use in this study. While this 

 method has the disadvantage of limiting flexibility of manipulation, 

 it has the advantage of brmging together in one place a permanent 

 assemblage of appendages for continued reference. The loss of time 

 and the risk of losing pertinent appendages in remounting are, there- 

 fore, elimmated. A further advantage is that appendages are cleared 

 sufficiently for critical observation within a short time after mounting. 



Several kinds of mounting media can be employed in making per- 

 manent slides. During this study I tried both Turtox CMC-10 

 (available commercially from General Biological Supply House, Chi- 

 cago) and Hoyer's Medium (see Baker and Wharton, 1952, for formula) 

 and found the latter to be superior for my purposes. Both of these 

 products, as well as a number of other types of nonresinous mounting 

 media, have the advantage of not requiring previous preparation of 

 material; thus appendages can be mounted directly from alcohol, 

 glycerin, M^ater, and similar preservatives. With either Hoyer's 

 Medium or CMC-10, the mounted media can be dissolved in water 

 and appendages then remounted if necessary. In mounting larger 

 appendages in Hoyer's Medium, large bubbles occasionally formed 

 and sometimes partially obscured the observation of a structure. In 

 most cases, however, troublesome bubbles were avoided by taking 

 extra care in mounting and getting the medium to proper viscosity. 

 A final step in preparing slide mounts from a water-soluble medium is 

 that of ringing the slide for permanency. Although a number of 

 products are advertised for this purpose on the commercial market, I 

 found ordinary fingernail polish adequate if applied at least twice after 

 the mount had sufficiently hardened. 



Several slides were prepared for each species. In instances where 

 large samples were available over a wide range, or where doubt still 

 existed as to the determination after examination with the dissecting 

 microscope, or where appreciable variation was indicated, larger 

 numbers of slide mounts were made for the species in question. All 

 drawings were made from slide-mounted appendages with the aid of a 

 Rayoscope microprojector (manufactured and distributed by R. D. 

 Gross, Delaware, Ohio). Fine details were added later with the aid 

 of a compound microscope. 



All measurements were made in millimeters with the aid of a 

 micrometer disc calibrated with a stage micrometer. Proportions 

 were either obtained from microprojector drawings or by use of an 

 ocular reticule. Total length as used herein refers to length of the 



