76 



are complete from side so side, are four in number. 

 The imperfect additional ones, vary from two to 

 four; the smallest and inner, consisting only of two 

 or three punctures. A plain edging includes the se- 

 micircle of punctures. In the beds of these casts, 

 the places of the punctures are shown by small coni- 

 cal elevations, and those of the ridges of the net-work, 

 by corresponding depressions." 



Should this prove to be a distinct species, we pro- 

 pose to call it Cryptolithus Bigsbii. 



The Nuttainia Concentrica of Professor Eaton seems 

 also very nearly allied to this species; he describes 

 it as having " four or five concentric arcs of punc- 

 tures in front of the buckler, separated by alternating 

 arc1fc>f fine elevated ridges." The genus Nuttainia, 

 to vpiich he refers this species, cannot include it, 

 and the N. Sparsa; for these two relics have scarce- 

 ly a single essential character in common; we have, 

 therefore, confined the genus Nuttainia, to the spe- 

 cies which he calls Sparsa. 



The Cryptolithus Tessellatus is very common at 

 Trenton falls. In the transition limestone at Glenn's 

 falls, in the state of New York, during a very short 

 visit to this place, Dr. R. Harlan procured a large 

 number of this fossil, but only the buckler, the 

 projecting front of which exhibited a pisiform pro- 

 tuberance above the level of the strata. Mr. 

 Eaton says that the N. Concentrica " occurs in the 

 wacke variety of transition of argillite, on the Cham- 

 plain canal," between the town of Waterford and the 



