UNIVERSALLY DISTRIBUTED SPECIES. 



73 



disappeared in one specimen ; the laterals bicuspid. He remarks that 

 every tooth of the radiila lies alone, so that even the cutting points do 

 not cover or disturb the basal surfaces, of the overlying rows. 



Schacko refers to the near alliance, in form of jaw especially, of H. 

 pygnuca with 21. mimitissima of the genns Pimctum of Morse. 



Looking at the descriptions and figures of the jaws of pygmcea and 

 minutissima, one will notice, with striking general similarity of char- 

 acters, some differences ; on the other hand, the lingual teeth of the two 

 forms appear to be the same, and the shells without variation of spe- 

 cific value. 



The facts regarding the distribution of S. pygmcea, which may be 

 treated as one of the circumpolar species, favor the opinion that Lea's 

 specific name must be placed in the synonymy of Punctum pygmwum. 



Moquin-Tandon describes the genitalia of the European form to have 

 neither dart nor multifid vesicles. 



Lately, in studying the jaw of Microphysa vortex from Florida, I have 

 become convinced that I was wrong in considering the jaw of pygmcea 

 to be related to that of the Orthalicidcc. It is quite similar to that of 

 Microphysa.! in which genus, accordingly, I place the species. 



The jaw is low, wide, slightly arcuate, with blunt, squarely truncated 

 ends ; it is composed of sixteen sepa- 

 rate pieces, each higher than wide, 

 with slightly overlapping edges. These 

 pieces do not run obliquely towards 

 the middle of the jaw ; there is, there- 

 fore, no appearance of an upper median triangular piece, as in Orthali 

 cus and Liguus. 



The lingual membrane is long and narrow. 

 1-13 teeth each. The centrals have a base 

 of attachment much longer than wide, ex- 

 panded below and squarely truncated, very 



Fig. 32. 



Jaw of M. pygmtea . ( M u rse . ) 



There are 54 rows of 13- 



FlG. 33. 



Lingual dentition of M. pygmcea. 

 (Morse.) 



much narrowed above, reflected. The re- 

 flection is very small, and has, according to 

 Morse, one single cusp ; but Schacko (Malak. 

 Bliitt., 1872, 178) describes the reflection in 

 some European specimens as tricuspid. Laterals of same form as cen- 

 trals, but with wider base of attachment in the first ones, and bicuspid 

 outer laterals much narrower. There are no distinct marginals. All 

 the teeth are decidedly separated, 



