472

CARBONIFEROUS STRATA,

represent the shell, looking at the sharp edge of the surface, or thesmooth rounded outline of the cast.

Locality—Tyrone, Derryloran (Cookstown). Sheet 29, No. 1,

Bellerophon recti-coslatus —(Portlock)—Plate XXXV., figs. 5 a, 5 b.

Cast widely umbilicated, back and sides obscurely ridged, apertureabout three times as wide as high; shell, of which a small portiononly remains, is T" thick; has a hand T2" wide, which is marked withstrong transverse, arched strife, from the ends of which proceed strong,straight (not curved as in B. hndcus, B. costatus,) stri* over the sides.The striae correspond nearly with those of B. costatus in strength, butby being straight and nearly perpendicular to the band, approximateto those of B. tangentialis (Phillips), from which species, however, thisis distinguished by the form of aperture. In respect to other species,the cast has some similarity to B. apertus (Sowerby), originally describedfrom a cast; but if the specimen of that species figured by Phillips becorrectly identified, this is distinct from it ; it is also wider inproportion to its length than in Sowerby’s figure, or in other castswhich seem to he clearly referrible to B. apertus. The difficulty ofrecognising species described solely from casts must necessarily begreat, and it is not improbable that two species are confoundedtogether as B. cornu arietis, just as two may have been so confounded inB. apertus : one of these appears to be more elongated and less widethan the other.

Locality—Armagh, in reddish limestone.

Orthoceras latissimum —Plate XXXV., figs. 2 a, 2 b.

For description see pa ge 390. Fig. 2 b represents an external viewof the shell, and fig. 2 a a polished section, in which the lateralsiphuncle may be obscurely traced.

Orthoceras maximum —(Munster)—Plate XXXV., fig. 3.

For description, see page 3S8. This represents a polished section,showing the peculiar structure of the siphuncle noticed by Munster. Itis from a much smaller individual, but in this respect it seems impos-sible to draw the line of specific distinction, and it cannot be doubtedthat different names have been given to the same species, when seen mdifferent stages of growth.

Posidoxojiya complanata —(Portlock)—Plate XXXIV., fig- 12.

Very minute, having, at first sight, much of the aspect of a Cyp ris >transverse, the beaks nearly obsolete, and close to one end; inequivalve,one valve slightly convex, though much depressed; the other quite flat,and, as it were, set into the larger like a Pandora; hinge line nearlystraight, surface marked by fine concentric lines of growth. The mag