1.35 



Orthonema quinquecarinata, (De Kon. sp.) 

 PI. IL, figs. 6, 6a, 6b, 7. 



Murchisonia quinquecarinata, L. G. De Koninck, i88i. Antiales 

 du Musee Royal UHistoire Naturelle de Belgique, T. viii., 4me 

 Partie, p. 23, PI. xxxiv., fig. 14, 15, 16. 



Shell elongated, turreted, composed of from thirteen to fifteen 

 gradually-increasing angular whorls. Each whorl is ornamented 

 with five keels, of which the middle one is placed rather below the 

 centre, and it is the most prominent. On full grown shells the 

 widest space is generally between the uppermost keel and that 

 next below ; specimens of about ten whorls frequently have the 

 spaces between the keels nearly equal ; and small shells have the 

 widest space between the central keel and that next above. Occa- 

 sionally the uppermost keel is faint, or absent altogether. In 

 addition to the five keels, M. L. G. De Koninck describes two 

 more below on the body whorl ; but there is not more than one 

 extra keel on any of my specimens. There is also, on some speci- 

 mens, a fine line between the central keel and that next above on 

 all the whorls. The lines of growth are distinct on many specimens ; 

 they are nearly straight, and they pass over the keels without any 

 indication of a sinus. Some of the lines are so strong as to cause 

 the keels to be somewhat crenulated on some specimens. Mouth 

 imperfectly preserved ; it appears to be rather longer than wide, 

 and the peristome is incomplete. No umbiHcus. 



I sent a specimen of this shell from Penton, and also of one 

 from Mosedale, to M. L. G. De Koninck, who kindly identified 

 them with his Murchisonia quitiquecarinata. In the Annales du 

 Musee Royal D'Histoire Naturalle de Belgique, T. viii., 4me Partie, 

 p. 14, he states that some of the shells described as Murchisonia 

 may possibly prove to belong to the genus Orthonema; but owing 

 to the imperfect preservation of some of them, he was unable to 

 decide this question. The preservation of the lines of growth on 

 the specimens from Penton proves that this surmise is correct, for 

 the outer lip, as indicated by the lines of growth, must have been 

 .entire, and these shells, therefore, can no longer be retained in the 

 genus Murchisonia. 



