72 A MANUAL OF AMERICAN LAND SHELLS. 



Mdchoire large de 0.25™°*, peu arqu^e, mince, k peine corn6e, transparente, assez 

 facile k 6tudier k cause de la transparence des t6gumeuts ; extr6mit^8 amincies ; partie 

 moyenne du bord libre un peu surbaiss6e ; cdtes verticales nombieuses, fines, serr^es ; 

 cr^nelures tr^s petites. 



In W. G. Binney's Synopsis (Smith. Inst. Coll., p. 4, December, 1863) 

 Hyalina (Conulus) minutissimaj Lea, is enumerated, and Tryon (Amer. 

 Journ. Conch, II, p. 257, 1866) placed the species in Conulus, while 

 quoting the particulars given by Morse of the jaw. 



In 1868 Lindstrom (Gotlands Nut. Moll., Taf. HI, Fig. 12) published 

 figures, but without description , of the jaw of H. pygmcea. On compari- 

 son of this with Morse's figure of minutissima, the identity of the two 

 species could scarcely be inferred. 



In Land and Freshwater Shells (Part I, p. 221, 1869) Functum, 

 Morse, is adopted as the generic name of Lea's species, treating that 

 genus as belonging to Orthaliciricn, by reason of the supposed structure 

 of the jaw. 



W. G. Binney (Invert. Mass., 2d ed., p. 403, Fig. 665, 1870) has Hya- 

 lina minutissima as occurring in Massachusetts, adding in a note, "The 

 character of the jaw would place tue species in the subfamily Orthali- 

 cinw, as a distinct genus, for which Morse's name Punctum might be 

 retained ; otherwise the species would be placed in Hyalina^ 



Mr. J. Gwyn Jeffreys (Ann. and Mag. ISTat. Hist., October, 1872) refers 

 to Hyalina minutissima as being identical with Helix pygmceaj Drap. 



Dr. G. Schacko (Malak. Blatt., p. 178, 1872) described both jaw and 

 lingual teeth of H. pygmoia, showing that both have the same charac- 

 ters as ascribed by Morse to Functum minutissimum. 



The following is a translation of Schacko's description of the jaw of 

 H, pygmcea : 



The jaw cousists of nineteen plates, which are grouped in the form of a horseshoe. 

 They lie together like the tiles of a roof, and partially cover one another. The plates 

 are connected by a tine transparent membrane. The middle plate, which is the largest, 

 and perfectly straight at the top, lies entirely alone, so that a space is visible between 

 it and the two next side plates. These are smaller and of the same length, while the 

 top is slightly curved. The plates have the same form as regards their length, but 

 the curve increases towards the cud plates. The third plate from the middle begins 

 to cover the second, the fifth covers half of the fourth, and the succeeding plates 

 always more, until the last covers two-thirds of the preceding one. 



The formula of the lingual membrane is given by Schacko as 

 being 114 rows of 19-1-19 ; by Morse, of Lea's species, 51 rows of 

 13-1-13. 



The centrals of H. pygmwa are said by Schacko to be tricuspid; the 

 two side cusps so small and scarcely recognizable that they entirely 



