PLEUROTOMARIID. 319 
margin. The part of the slit which has been progressively filled 
up forms a band round the whorls. 
PTYCHOMPHALUS, Agass. (Crypteenia, 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 Pleurotomariz. Species 
numerous, Liassicto Cretaceous. P. striatus, Sowb. (1xxxii, 86). 
LEPTOMARIA, Desl., 1865. Shell subturbinate, rather thin, gen- 
erally ornamented with very numerous, subequal spiral striz, band 
very narrow, placed near the middle of the whorls, slit in the 
outer lip very deep, axis solid or hollowed out. Mostly ereta- 
ceous to tertiary. P. amena, Desl. 
MorcuisoniA, d’Archiac. 
Htym.—Named in honor of Sir Roderick I. Murchison. 
Distr.—Fossil,50sp. L. Silurian to Permian; North America, 
Europe. JL intermedia, Verneuil (1xxxii, 86). 
Shell elongated, many-whorled; whorls variously sculptured, 
and zoned like Pleurotomaria; aperture slightly channeled in 
front; outer lip deeply notched. 
‘The Murchisonie are characteristic fossils of the paleozoic 
rocks; they have been compared to elongated Pleurotomarie, 
or to Cerithia with notched apertures; the first suggestion is 
most probably correct. 
MURCHISONIELLA, 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. 
Porcetiia, Léveille. 
Distr.—10 sp. U. Silurian to Trias. Europe. P. Puzo, Lev. 
(isxxii, 87). 
Shell symmetrical, discoidal or planorbiform; periphery with 
a deep, marginal slit. 
PotyTREMARIA, d’Orb. 
Syn.—Trochotremaria, Ryckh. 
Distr.—Carboniferous; Belgium. P. catenata, Kon. (1xxxii, 88). 
Shell turbinated, heliciform, periphery pierced by a line of 
non-tubular perforations. 
CaTantostoMa, Sandberger. 
Distr.—Devonian, Trias. C. clathratum, Sandb., (1xxxii, 89). 
Shell turbinate, heliciform or bulimiform; last whorl deflected ; 
the peristome incomplete, irregular, slightly varicose on the last 
