234 AMERICAN JOURNAL 



terior surface of the liver ; in the latter there is no cervical 

 branchia, the muzzle has no frili, there are two renal organs 

 (according to Mr. Lankester), the crop is frequently large and 

 prominent, and the radula is coiled on the anterior under surface 

 of the liver. The branchice are subject in this suborder to the 

 most extraordinary variations. 



It will be noticed that the accompanying figures of Collisella 

 testudinalis and Patella vuhjata differ from those of Gray and 

 Loven. The reason of this is that in the first case the long cusps 

 of Gray's figure are due to the fact that they are broken down 

 upon the cusps of the other laterals, instead of being represented 

 in their natural positiom In the case of Patella vulgata, strange 

 as it may appear, though it has been often figured, I have not 

 been able to find a single figure which expresses all the charac- 

 ters distinctly. Wilton's, in Woodward's Manual, is in some 

 respects the best, but the tri dentate cusp of the third lateral is 

 so rendered that it appears as if it belonged to two teeth, and 

 the uncini are poorly shown. Loven's figure is worse, but his 

 figure of the teeth of Acmoia virginea is very good, and bears 

 comparison with the object itself. 



Care should be taken in figuring the dentition of any of the 

 Docoglossa not to break down or crush the long slender cusps, 

 or to confound the bosses which ornament the area with true 

 cusped teeth. Bosses often occur, even on the pleura, without 

 any tooth or cusp at all, and this should be carefully noted, but 

 not incoi'porated into the formula. The central line is frequently 

 indicated by an elongated narrow boss between the inner late- 

 rals, which is however barely perceptible and never carries a 

 cusp. It is undoubtably the homologue of the rhachidian tooth, 

 which only appears in this family in the single genus Ancistro- 

 mesus. A sharp lookout should be kept for the minute uncini 

 figured in Collisella, which are as readily overlooked. 



The reader will notice a wholesale consolidation of generic 

 names founded on trivial, inconstant and imaginary characters; 

 yet, whenever practicable, the old and familiar names have been 

 retained. In many cases, however, they have become so involved 

 in a tissue of errors and confusion that it has been no easy mat- 

 ter to extricate the types and decide on their several claims. For 

 the old and new generic names adopted in this paper, tangible, 

 and it is to be hoped sufficient, characters have been given, in 

 most cases, for the first time. 



I have regarded as at least of subgeneric value decided differ- 

 ences in the branchiae, in the dental formula, and, when accom- 

 panied by other characters, such a difference in the shell as for 

 instance exists between Patella vulgata and Patina pellucida ; 



