12 PALEONTOLOGY OF NEW YORK. 



a specimen with abnormally thickened walls and great development of vesicu- 

 lar tissue. 



With all the material here illustrated on plate cxv, and much more before 

 me, I am unable to find any characters by which generic or specific distinction 

 can be drawn between the forms represented in figures 1 and 2 and all those 

 which follow up to figure 39. The names under which these and similar forms, 

 as before mentioned, have been described are: Spirorbis Cincinnatensis, Tmlacu- 

 lites incurvus, T. tenuistriatus, T. Oswegoensis, T. Sterhngensis and T. Richmondensis. 



Besides the species above enumerated, these organisms, in their different 

 phases of development, have furnished the basis for the establishment of the 

 genus Ortonia (O. minor and 0. corded), and a species described under Conchico- 

 i.rrr.s ((' corrugatus). The latter genus was founded upon a similar organism, 

 occurring in the Caradoc shales of Westmoreland, England, the equivalent, in 

 age, of the Hudson River group of America (American Journal of Science, 

 Third Series, vol. iii, p. 202. 1872). 



The manner of growth and development; the external form and internal 

 structure of these bodies, seem to demonstrate very clearly that they should be all 

 referred to the genus Cornulites, as described and illustrated by the author of 

 the genus and by subsequent authors whose opinions are entitled to respect. 

 The description and illustrations of Cornulites serpularius, Murchison (Silurian 

 System, p. 627, and plate xxvi, figures 5-9), present a most important study in 

 this connection, ami leave no doubt as to the nature of the organism under 

 consideration. 



In regard to the forms illustrated on plate cxv, figures 1-39, I do not propose 

 to recognize any distinction of species, and I leave them without prejudice to be 

 referred to such specific names as their authors may claim for the various phases 

 here represented. Though referring certain of the illustrations to the names 

 by which they are usually recognized, I have purposely confined myself to the 

 discussion of the various phases of what appears to me a single form of this re- 

 markable organism, all the specimens being from the same geological horizon. 



Figure 10 represents the earlier stages of an irregular group growing upon 

 the shell of an Orthoceras, from the (Jtica slate of New York, and which pre- 



