92 



PAL^ONTOLOGT OF NEW-YORK. 



All the specimens of this species which have fallen under my observation are casts, and 

 these have often been much compressed ; and, as they are usually replaced by siliceous material, 

 they are rough and irregular. I have referred the species to Murchisonia, to which genus it 

 more probably belongs than to Loxonema. In the specimen figured by Mr. Conrad, there are 

 a few folds on the last volution, but these are not the remains of strige ; and since we do not 

 yet know of the existence of a true Loxonema in the middle silurian period, we should re- 

 quire unequivocal proofs of its character before referring a specimen from this geological 

 position to that genus. 



Fig. 7 a. A young specimen of this species. 

 Fig. 7 b. An older specimen of the same. 



Fig. 7 c, d. Two specimens of the largest size observed ; the last one wanting one or more of 

 the upper volutions. 



Position and localities. The smaller individual^ of this species occur in the shale below 

 the ore bed in Wolcott ; and the larger specimens have been found at Medina, Orleans 

 county, and at Reynale's basin in Niagara county. {State Collection.) 



487. 8. BUCANIA STIGMOSA {n. sp.). 



Pl. XXVIII. Fig. 8 o - c. 

 Compare Bucania puncUfrons, Pal. N. York, Vol. i, pag. 187, pl. 40, fig. 1 a, h, c, d. 



Convolute, suborbicular ; volutions - ?, somewhat rapidly enlarging towards the aperture, 

 which is abruptly expanded with a sinus on the dorsal margin ; back of the shell rounded, 

 with a sharp carina along the centre ; sides of the volutions somewhat rounded, and abruptly 

 depressed into a deep umbilicus ; surface marked transversly by elevated lines, diverging and 

 ascending from the carina, and arching over the side into the umbilicus ; longitudinally marked 

 by elevated lines parallel to the carina ; intermediate spaces rhomboidal or oval. 



This shell resembles in its general character B. punctifrons of the Trenton limestone, and 

 possesses characters intermediate between that species and B. sulcatina. 



The surface of this species is regularly decussated by arching transverse and longitudinal 

 striae, leaving rhomboidal spaces between them. Where these elevated lines are somewhat 

 worn, the spaces appear like oval depressions or scars, with the separating lines not strongly 

 defined. In this condition the surface resembles B. punctifrons ; but in all the specimens of 

 that shell examined, there are no direct longitudinal striae visible, and the arching transverse 

 ones are very inconspicuous ; the puncta, moreover, are proportionally smaller than in the 

 present species. 



The casts of this species, where the last volution is incomplete, are scarcely distinguishable 

 from B. punctifrons. The species is quite rare, and all those observed are more or less 

 imperfect. 



