OF CONCHOLOGY. 279 



Nothing is said about the extent of the branchiae in the diagno- 

 sis, but they appear by the figure to be interrupted behind the 

 head. 



Helcioniscus exaratus, Nutt. Plate 16, fig. 29. 



Patella exarata, Nutt., Jay's Cat., p. 38. Rve. Conch. Icon. 



pi. xix, fig. 47, a, b, 1854. 

 Patella sandivicensis, Pse., P. Z. S., 1860, p. 437. 

 Patella undato-Urata, Pse., ubi ? MSS. label. Cab. S. I. 



Mantle margin broad, thick, strongly crenate, conspicuously 

 papillose. Sides of foot smooth, blackish. Tentacles stout, 

 rather long ; muzzle papillose around the edges. Head small, 

 short. BranchiiTe interrupted between the muscles in front, close, 

 prominent. Foot stout and muscular. General coloration dusky, 

 lighter in the commissures. Anal and other papilk« short but 

 prominent. Inferior nuchal commissure deep and straight. 

 Formula, ." 



3(2— 1-1— 2)3 



Hah. Sandwich Islands, Pease, Garrett. 



The so-called species of Mr. Pease are not even distinguish- 

 able varieties, and have no characters by which they can be dif- 

 ferentiated from the typical exarata. The description of the 

 first is in English, without a figure. I have not been able to find 

 a description of the second. 



Genus PATINA, Leach. 



Patina, Leach, MSS, 1819. Gray, Syn. Brit. Mus., 1840. 



Moll. Gt. Brit., 1852, p. 223. Guide, Moll., p. 175. 



Syn. Brit. Mus., Ed., 1842, p. 90. 

 Patella, Loven, Ofv. K. Vet. Ak. For., 1847, p. 198. 

 < Nacella, H. & A. Ad. i, p. 467, 1854. Chenu, Man. de Con- 



chyl., i, p. 378. Woodw. Man., p. 155. Cpr. Lect. Moll., 



p. 72. 

 Helcion, Jeffreys, Brit. Conch., iii, p, 242. (Not Montfort.) 

 Ansates, Sby., Conch. Man. Ed. ii, p. 68, 1842. (Not Klein.) 

 ? G-onicUs, Raf. (See Syn. Patella.) 



Animal with the branchial cordon interrupted in front ; teeth 

 with the inner two series parallel, third series with a lai'ger den- 

 ticulate cusp, posterior ; radula furnished with three uncini on 

 each side. Formula, ^ Shell with the apex subter- 



' 3(J^-2-2-i^)3- _ _ ^ 



minal, anterior; smooth, thin, semi-pellucid or horny in texture. 



Should the details of the soft parts and dentition of Helcion 



(pectinatus) prove on examination to agree with those of the 



