218 SOLARIID. 
carina the basal margin of the aperture is deeply flexuously 
emarginate ; above the carina it is again, but less deeply, emar- 
ginate, then sweeps forward roundly, and then slightly recedes 
before joining the preceding whorl. This curious form belongs 
in all probability to the Solariide, representing among them 
Basilissa among the Trochide, and recalling Platyschisma, but 
with a different aperture. When perfect, the margin at the 
carina must project forward like a claw or nail, as in Schizos- 
toma. When adult, the nuclear whorls are filled up with a solid 
deposit of shelly matter, and it is probable that there is a slight 
notch at the end of the umbilical rib. S. brunnea, Dall. West 
Indies. 
PLatyscHisMA, M’Coy. 
Disir. — Silurian—; U. 8., Europe. P. Uchtensis, Keys 
(bxvyiT): 
Shell depressed trochiform, whorls somewhat rounded, orna- 
mented with small transverse ribs; spire short, whorls few ; 
aperture oblique; umbilicus small, rounded. 
ARCHITEA, Costa. 
Syn.—Trachysma, Jeffreys. 
Distr.—A. delicatum, Phil. (xv. 8). 
Shell turbinate, but little elevated, thin, widely and deeply 
umbilicated below; aperture rounded, peristome continuous, 
simple. Operculum corneous, pellucid, spiral, flattened and 
smooth on the outer side, the spire slightly prominent in the 
centre of the inner side. 
STRAPAROLLUS, Montfort, 1810. 
Syn.—EKuomphalus, Sowb. Helicotoma, Salter. Pleuronotus, 
Hall. Helicites, Schloth. Centrifugus and Inachus, His. 
Cirrus, Sowb. Phanerotinus, Sowb. (partim). Omphalocirrus, 
Planicirrus, Echinocirrus and Trochocirrus, Ryckholt. Omphal- 
otrochus, Meek. Phymatifer, Kon. Straparollina, Billings. 
Distr.—b60 sp. Lower Silurian to Trias; United States, Europe, 
Australia. S. Gualteriatus, Vern. (ixv, 9). S. calcar, d’Orb. 
(Ixv, 21). 
Shells depressed, whorls angular or carinated, aperture sub- 
quadrangular, umbilicus wide, conical. Opercuium shelly, multi- 
Spiral. 
It has been proposed by several conchologists to unite the 
genera Straparollus (— Euomphalus) and Solarium in one. 
When, however, we compare the large number of species of both 
these genera, it appears that the smooth or at least less orna- 
mented surface of the shell, the constant want of a distinctly 
crenulated margin round the umbilicus, combined with the 
roundish form of the whorls of Straparollus, make its separation 
