GASTEROPODA.] UPPER PALZOZOIC MOLLUSCA. 527 
regular, oblique lines ; those extending from the band to the umbilicus on the base of the body-whorl are obtuse, 
irregular, and slightly flexuous; most specimens shew five or six spiral strive beneath the keels on the body- 
whorl, and some shew traces of them above the band on the spiral whorls. Length one inch, proportional height 
25 50 
of mouth =, height of penultimate whorl =, diameter of base =, width of mouth =, diameter of umbilicus in 
casts =. 
Most specimens shew the transverse, sharp, regular, oblique striz very strongly marked, with no trace 
of spiral lineation. Specimens agreeing with my P. decussata as above have the surface regularly reticulated by 
nearly equal spiral and transverse strize, and such I considered at one time specifically distinct. Seeing, how- 
ever, in some of the Isle of Man specimens, traces of spiral strice on parts of the surface, and not on other parts, 
I venture to unite the species as varieties, the more readily as Prof. Phillips mentions in his original description 
that some specimens have spiral stric. 
Position and Locality— Not uncommon in the carboniferous limestone of Poolwash, Isle of Man. 
PLEUROTOMARIA CONSOBRINA (de Kon.) 
Ref. and Syn.—de Kon. Supp. Anim. Foss. Bel..p. 691 = Murchisonia angulata (Phill.) Portk. Geol. Rep. 
t. 31. f. 5 (not of Phillips). 
Dese.—Acutely conic; apical angle 55°; spire composed of six gradually increasing whorls, each very 
strongly angulated in the middle, where it bears a very prominent, thick, single keel, above (or behind) which 
the volutions are flat and sloping to the keel, beneath which they are gently concave and nearly vertical, 
or sloping slightly inwards to the suture; on the body-whorl a second thick ridge, or keel, appears below 
(or in front) of the former one, and slightly nearer to it than it is to the suture ; the second keel is exactly 
covered by the edge of the suture, and concealed in the whorls of the spire (in some states of preservation these 
two keels seem split into two or three very fine ones); base flattened from the anterior keel, slightly convex; 
umbilicus small, rounded, deep; surface marked with coarse, irregular, oblique strize, which arch backwards 
from the upper sutures, and rather strongly crenulate the mesial keel of the spiral whorls, below which 
they bend forwards, and on the body-whorl crenulate the anterior keel, and are then rather abruptly directed 
46 20 
into the umbilicus. Length of small specimen ten lines, height of last whorl 4, height of penultimate whorl =, 
width of base =, width of mouth ;5, width of umbilicus ;{;; length of large specimen one inch five lines. 
From the direction of the striz it would seem as if the sinus was obliquely angular, and occupied all the 
space between the two keels seen on the body-whorl. This species is so strongly marked that it is needless to 
point out its distinctions from any of the others, with the exception, perhaps, of the P. laticincta de Kon. which 
is distinguished by its less acute spire (if his figure be correct), also by its spiral strize and the two distant keels 
being visible on the spiral whorls. The shell is thick, and one of the specimens shews the nacreous inner layer, 
which militates against King’s approximation of the genus to Hmarginula, and favours d’Orbigny’s comparison 
with Haliotis. 
Position and Locality Not uncommon in the carboniferous limestone of Derbyshire. 
PLEUROTOMARIA DECIPIENS (J/°Coy). PI. 3. H. fig. 13, 14. 
Ref—M Coy, Ann. Nat. Hist. 2nd Series, Vol. XII. 
Dese.—Vax. a, Spire acute, regularly conic, apical angle about 40°, composed of about seven or eight 
gradually-increasing flat whorls; suture a simple impressed line ; base of body-whorl flattened, forming a strong 
angle with the spire; no umbilicus; pillar-lip slightly thickened, arched; mouth oblong, angulated, a little 
wider than long ; surface marked with narrow thread-like, spiral ridges, separated by flat or slightly concave 
spaces about three times their width; about eight or nine spiral ridges on each whorl, and seven or eight more, 
rather stronger, on the base; the intervening spaces very irregularly cancellated by obscure, unequal, obtuse, 
[pasc. ur. ] 3 Y 
