170 AMERICAN JOUKNAL 



are obliged to draw attention to are the result of a faulty method 

 of working and inexperience in handling the delicate and com- 

 plex structures which he has attempted to figure, rather than any 

 want of care on his part. 



Fig. 1, S. NuttalUi, and fig. 2, B. pallidior, are probably cor- 

 rect, though " d," in the first named figure, is exceedingly ob- 

 scure, and we cannot believe that it is a satisfactory view of the 

 8th lateral, which it claims to represent. Fig. 3 is supposed to 

 represent some of the teeth of Cysticopsis tumida. It is some- 

 what obscure, so that its true relations cannot be determined 

 from the figure. This is a very interesting species, and it is a 

 pity that a clear and comprehensible figure of its dentition was 

 not given. Figs. 4, 5 and 6 Avere drawn by Dr. Leidy, and, 

 though engraved in a manner which is not adapted to give a good 

 idea of the teeth, especially the bases, yet they are probably 

 pretty correct, while it must be remembered that they were drawn 

 twenty years ago. The central tooth of fig. 6 {Li77iax flavus), 

 does not agree with Morse's figure to which Mr. Binney refers. 

 The latter is most probably the more correct of the two, if they 

 were both obtained from the same species, which would seem 

 doubtful. The figure of Melawpus hidentatus^ Say, bears in- 

 trinsic evidence of general correctness, though poorly drawn and 

 possibly not exact in detail. The figure (No. 8) of Helicina 

 occulta, Say, is very bad and quite erroneous. We have exam- 

 ined some of the specimens collected by Mr. Leland, from among 

 which Mr. Binney obtained the radula here figured, and Avhich 

 were labelled by the latter gentleman as Helicina occulta. The 

 central tooth is quite destitute of denticles, is of a different shape 

 from that given in fig. 8, and the lateral teeth diff"er in many 

 particulars. The uncini have not the hoe-like form of those in 

 the figure. 



On the whole, the radula strongly resembles Troschel's figure 

 of the dentition of H. orbicidata, Binn., (If. trossica, Troschel,) 

 but the central tooth is proportionally larger and the laterals 

 differ in minute details. No true Helicina yet examined, has a 

 denticulate median tooth, and this should have put Mr. Binney 

 on his guard. The only conjecture we can offer as to the cause 

 of the error is that it might have been a broken and worn an- 

 terior tooth, or the false appearance of denticles might have been 

 caused by the refraction of too strong a light used during the 

 examination. The radula has been examined by several com- 

 petent naturalists, and there can be no doubt as to the edentu- 

 lous character of the median tooth. 



Fig. 9 {PompJiolyx effusa) is also exceedingly erroneous. 

 We are indebted to the extreme courtesy of Mr. Binney for a 

 fresh specimen of the typical effusa,' and for the opportunity of 



