MANUAL OF THE MOLLUSCA. 
OPHILETA, Vanuxem (p. 267), was founded on species of 
Maclurea, with very slender whorls. Mr. Billings regards them 
as distinct, and distinguishes them as follows :—‘‘ In Maclurea 
the aperture is entire, and the whorls usually large, but in 
Uphileta it has a sinus below and a notch aboye, while the 
whorls are usually more slender. 
‘In Maclurea crenulata (Billings) there is a sort of spiral band, 
and also there are indications of a sinus in the lip on the flat 
side, but they are only incipiently developed.”’—(Billings.) 
STROPHOSTYLUS, Hall. 
Etymology, strepho, I turn, and stylus, columella. 
Shell subglobose or ovoid ; spire small, body whorl large and 
ventricose; outer lip thin; columella twisted or spirally grooved 
within, not reflected; umbilicus wanting; aperture ovate or 
transversely oval; apparently related to Platystoma. 
Distribution, 10 species. Silurian. United States. 
HELIOcRYPTUS, D’Orbigny, 1850. 
Shell depressed, orbicular; whorls embracing; umbilicated 
on both sides; aperture vertical, oval transverse. 
Distribution. H. pusillus, Coral Rag, France, Germany ; 
H. radiatus, U.G.S. Blackdown, Mans. 
[FamiIty JANTHINIDE | 
Includes— 
JANTHINA and RECLUZIA (see p. 285). 
Faminty XII.—CALYPTRAIDZ.* 
PLATYCERAS, Conrad, 1840 (see p. 277). 
Type, Pileopsis vetusta, Sowerby. 
Synonyms, Acroculia, Phillips, 1841; Orthonychia, Hall, 1843. 
Shell depressed, subglobose to oblique, subconical; spire 
small; whorls few, free or contiguous; aperture more or less 
expanded, often campanulated, entire or sinuous. 
Many species show asinuosity of the strize, indicating a notvh 
in the margin of the aperture during the first stages of growth, 
Mr. Hall has been unable to recognise the peculiar muscular 
impressions which are characteristic of Pileopsis. Specimens of 
éume species show the expansion of the columellar lip, and its 
partial or entire union with the yolution, presenting all the 
* See p. 278. 
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