230 AMERICAN JOURNAL 



This supposes that all the teeth are in one transverse line, but 

 •when, as in many patellse, some of the laterals are in a series in 

 advance of the rest, a ^ninus sign would serve to indicate their rela- 

 tive position in substitution for the jylus sign ; as, o 



■3(]-f.f->)3 

 would signify a radula without a median tooth, in which the two 

 simple inner lateral teeth on each side are in advance of the 

 three cusped third lateral, and wliich was provided with three 

 uncini. The advantage of the system is evident, from the small 

 space in which a large amount of information can be compressed 

 and yet remain perfectly comprehensible. It is true that it is 

 slightly more complicated" th;in that in use at present, but hardly 

 so to an objectionable extent. When the cusps are quite simple 

 the fractional form of the formula for each tooth may be dis- 

 pensed with. The method thus indicated will be used through- 

 out this paper. 



General Remarks. 



The dentition of the Docoglossa vera, has certain well marked 

 characteristics not common to other groups. The radula is 

 usually jointed, or rather divided by impressed transverse lines 

 between each series of teeth and its neighbors. This flat section 

 I shall term, for convenience, the area. The area is bounded 

 on each side by a narrow smooth pleura, upon which the uncini 

 are situated, if any exist. Upon the area are certain solid, 

 more or less thickened, plates or bosses, of intricate form ; gen- 

 erally, but not always, bearing teeth. These bosses are some- 

 times translucent, but are usually more deeply colored than the 

 area, upon which they are solidly fixed. Upon the bosses are 

 found strong, recurved, hooked teeth, almost invariably black 

 and opaque. The teeth are readily detached from the bosses ; 

 in fact, with specimens long preserved in alcohol, it is difficult 

 to obtain any part of the ribbon with the cusps undisturbed, 

 while the bosses cannot be detached from the area by any means 

 short of the destruction of both. The radulse of this group are 

 apparently less purely chitinous than those of the Pulmonata, 

 MhacMglossa, &c., as they cannot be boiled in potash for an in- 

 stant without detaching all the cusps from the bosses, and in a 

 very short time the greater portion of the radula itself will be 

 destroyed. Even soaking in a weak potash solution, quite cold, 

 in order to cleanse the structure, must not be long protracted, 

 or the latter will become disorganized. All the species are fur- 

 nished with a more or less cartilaginous jaw, which is also de- 

 structible in potash. 



The Docoglossa, as a group, manifest what may be termed a 



