346 



PALEONTOLOGY OF NEW-YORK. 



710. 21. MURCHISONIA BOYDII. 



Pl. LXXXIII. Fig. 3. 

 Loxonema boydii. Report on the 4lh Geological District of New-York, 1843, p. 138 ; fig. 3, p. 137. 



Spire moderate ; volutions about six, gradually enlarging to the last one, which is somewhat 

 ventricose ; umbilicus small. 



The few impressions of striae remaining upon the cast are not sufficient to decide whether the 

 fossil be a Loxonema or Murchisonia ; and since all the Gait specimens, which are of the same 

 age, appear to belong to Murchisonia, I have concluded to refer this one to the same genus. 

 This species approaches in form to M. loganii, but is much smaller, and the volutions slightly 

 more oblique. 



Position and locality. In the argillaceous limestone near the base of the Onondaga-salt 

 group, Newark, Wayne county. I have also obtained at Gait, fragments of a species undis- 

 tinguishable from this one. 



711. 22. MURCHISONIA LOGANII (n. sp.). 



Pl. LXXXIII. Fig. 4 a,?). 



Subfusiform ; spire elongated, consisting of about eleven or twelve volutions, which increase 

 somewhat rapidly in size from the apex ; last volution expanding towards the aperture ; co- 

 lumella large, without fold or carina ; surface markings unknown. 



This species is readily distinguished from either of the preceding, by the more rapid enlarge- 

 ment of the volutions, as well as their smaller number. The centre is traversed by a large 

 columella, which opens in an expanded umbilicus. I have not been able to discover the evi- 

 dences of a carina in the moulds, since, they are so thickly studded with minute crystals of 

 calcareous spar as to obliterate or obscure any such marking. The volutions in the cast are 

 more regularly rounded or ventricose than in the preceding species, and, in those I have 

 examined, retain no impression of carinse or strise. 



Fig. 4 a. A specimen, the upper part of which is a mould of the shell, while the lower part 



preserves the cast of the interior with some portions of the shell and columella. 

 Fig. 4 i. A cast preserving several volutions below the apex. 



Position and locality. In the limestone at Gait, Canada West. 



712. 23. MURCHISONIA MACROSPIRA {n. sp.). 



Pi,. LXXXIII. Fig. 5. 



The specimen consists of the mould, showing the impression of four and part of the fifth 

 volution, marked by a strong carina along the centre ; last volution showing a large canal 

 extending downwards in the direction of the spire. 



This species is larger and stronger than the preceding. 



Position and locality. In the limestone at Gait, Canada West. 



