PLEUROTOMARIID^. 319 



margin. The part of the slit which has been progressively filled 

 up forms a band round the whorls. 



PTYCHOMPHALUS, Agass. (Crvptasnia, Desl.) Heliciform or 

 trochiform shells, with an almost smooth surface, a thick callosity 

 covering the umbilical region and a distinct band on the posterior 

 portion of the whorls, terminating at the aperture with a short 

 slit, sometimes a simple fold. The smooth surface and umbilical 

 callosity distinguish it from other Pleurotomarise. Species 

 numerous. Liassic to Cretaceous. P. striatus, Sowb. (Ixxxii, 86). 



LEPTOMARIA, DcsL, 1865. Shell subturbinate, rather thin, gen- 

 erally ornamented with very numerous, subequal spiral striae, band 

 very narrow, placed near the middle of the whorls, slit in the 

 outer lip very deep, axis solid or hollowed out. Mostly creta- 

 ceous to tertiary. P. amcena, Desl. 



MuRCHisoNiA, d'Archiac. 



Etyni. — Named in honor of Sir Roderick I. Murchison. 



Distr. — Fossil, 50 sp. L. Silurian to Permian ; North America, 

 Europe. M. intermedia, Verneuil (Ixxxii, 86 ). 



Shell elongated, many-whorled ; whorls variously sculptured, 

 and zoned like Pleurotomaria ; aperture slightly channeled in 

 front ; outer lip deeply notched. 



The Murchisoniffi are characteristic fossils of the palaeozoic 

 rocks; they have been compared to elongated Pleurotomarise, 

 or to Cerithia with notched apertures ; the first suggestion is 

 most probably correct. 



MURGHISONIELLA, Morch. A single living species is referred to 

 this uncharacterized group. West Indies. 



DisoTEKA, Gardner, 1880. Differs from Murchisonia in having 

 two slit-bands, Cret. ; England. 



PoRCELLiA, Leveille. 



Distr. — 10 sp. U. Silurian to Trias. Europe. P. Puzo, Jjev. 

 (Ixxxii, 87). 



Shell symmetrical, discoidal or planorbiform ; periphery with 

 a deep, marginal slit. 



POLYTREMARIA, d'Orb. 



Syn. — Trochotremaria, Ryckh. 



Distr. — Carboniferous ; Belgium. P. catenata, Kon. (Ixxxii, 88 ). 

 Shell turbinated, heliciform, peripher}^ pierced by a line ol 

 non-tubular perforations. 



Catantostoma, Sandberger. 

 Distr. — Devonian, Trias. G. clathratum, Sandb. (Ixxxii, 89). 

 Shell turbinate, heliciform or bulimiform ; last whorl deflected ; 

 the peristome incomplete, irregular, slightly varicose on the last 



