THE JAW AND LINGUAL MEMBRANE. 49 



cal genera.) Vilrina, 1 Vitrinoidea, 2 Vitrinopsis 3 Nanina* and all the 

 genera -now recognized in its disintegration, Stenopus, 5 Vitrinoconus,* 

 Macrocyclis? Zonites. 6 



The following genera have quadrate marginal teeth. They may be 

 readily grouped by the character of their jaw, which is either in one 

 single piece (A), in one single piece with an accessory upper quadrate 

 piece (), or in numerous pieces (C). 



A. Those whose jaw is in one single piece may again be subdivided 

 into several groups based on the absence, presence, and peculiarities of 

 the ribs on their jaw. This division, however, is unsatisfactory, as 

 these characters are not always well marked. 



(a) Jaw without ribs: Philomycus? Parmella? 10 Oopelta, 11 Sagda, 13 

 Patula, 13 Polymita, 1 * Hemitrochus, 15 Helicodiscus, 16 Onchidella, 17 Acavus, 

 Corilla, Caryodes, Panda, Labyrinthus, Caracollits, ls Leucockroa, 19 Cysti- 

 copsis ? 20 Plagioptycka,*^ Leptoloma? 2 Anostoma, 23 A nostomella ? 24 Tomigerus 1 

 Boysia ? Plectostoma ? Hypselostoma ? 25 Achatinella, 26 Clausilia^ 1 Steno- 

 gyra, StrophiaJ* Bidiminus, Balea 31 Pupa, 82 Vertigo, 33 Ferussacia, 84 

 Ccecilianella, 35 Geostilbia? Azeca ? Tornatella ? 36 Zospeum ? 87 Holospira, 33 



l See this work. Semper, 1. c. 85, PI. IX. Fig. 33. 



8 Ibid. 86, PI. XI. Fig. 26. * Ibid. 



6 Bland, Ann. Lye. N. H. of N. Y., VIII. 158, Fig. 



6 Semper, 1. c. 91, PI. XI. Fig. 27. 7 See this work. 



8 See this work. ' 9 See this work. 



1 .law and lingual dentition unknown. 

 H Heyneinaun, Malak. Blatt., XIV. PI. I. 2. 



12 Bland and Binney, Am. Journ. Conch., VI. 177. ls See this work. 



" Bland and Binney, Ann. Lye. N. II. of N. Y., X. 341, PL XVI. Fig. 1. 

 16 See this work. 16 See this work. 17 See this work. 



18 See Semper, 1. c. No doubt other genera of disintegrated Helix will be found to be 

 grouped here. I propose at present to remove from Helix all the species not having ribs 

 upon their jaw. 



19 Bland and Binney, Ann. Lye. Nat. Hist, of N. Y., X. 220. 



20 Ibid., IX. 



21 Proc. Ac. Nat. Sc. Phila. 1874, 56. "2 Ibid. 58. 



23 Journ. de Conch., XIX. 261, PL XL Fig. 4. 



24 Jaw and dentition unknown. 



25 Jaw and dentition unknown. 



26 Bland and Binney, Ann. Lye. N. H. of N. Y., X. 335, PI. XV. Figs. 6, 7. 



27 Troschel, Moquin-Tandon, Lehmann, etc. 



28 See this work. 29 See this work. 

 8 But some species have ribs. See Moquin-Tandon, Lehmaim, etc. 

 si Moquin-Tandon, Moll. Fr., PI. XXV. Fig. 6. 



82 See this work. 83 gee this work. 8 See this work. 



86 See this work. 88 Unknown. 



87 Heynemann, Mai. Bl., X. PL III. Fig. 14. Jaw unknown. 



88 See this work. 



