Descriptions of new species of Leptocna and Cyclonema. 153 



revolving lines, varying in size and distinctness, in some examples being 

 sharp and prominent, in others scarcely visible to the naked eye, 

 crossed by fine strise, or lines of growth, ■which, to the sharply defined 

 ones, give the shell a beautifully ornamented appearance. Volutions 

 with oblique undulations, and a broad revolving depression near or 

 above the center, most conspicuous on the body whorls, sometimes 

 extending to the apex. 



Height of a large specimen about IJ inches, bi'eadth 1^ inches. 

 Small ones, less than f ths of an inch in height and breadth. 



The above is the typical form, but examples are found vaiying 

 gradually to a narrow body whorl, narrow, shallow suture, and conical 

 form, and decidedly longer than wide ; all having the peculiar wavy 

 or undulating surface more or less distinct, with other features in com- 

 mon, so that it is impossible, or very difficult, to find a dividing line. 



Figures 5e, 5/*, and 5g, plate 13, Paleeontology of Ohio, vol. i., 

 part 2, show the extremes of this species. 



Position and locality : Lower Silurian formation, upper part of the 

 Cincinnati Group, Warren and Clinton counties, Ohio, and other local- 

 ities in Ohio and Indiana. 



Nullipores — (U. P. James.) 



I have occasionally found, during years past, a thin substance cover- 

 ing surfaces of our fossil corals, clusters of crinoidal columns, etc. (of 

 the Cincinnati Group), that Palasontologists, whom I have consulted, 

 could not explain. The following extract from Dana's work on Corals 

 and Coral Islands, published 1872, seems to throw some light on this 

 obscure fossil form : 



" Nidlipores. — The more important species of the vegetable king- 

 dom that afford stony material for coral reefs are called Nullipores. 

 They are true Algje, or sea-Aveeds, although so completely stony and 

 solid that nothing in their aspect is plant-like. They form thick, or 

 thin, stony incrustations over surfaces of dead corals, or coral rock, 

 occasionally knobby or branching, and often spreading lichen-like. 



" They have the aspect of ordinary corals, especially the Millepores, 

 but may be distinguished from these species by their having no cells, 

 not even any of the pin-punctures of those species. 



" Beside the more stony kinds, there are delicate species, often 

 jointed, called Corallines, which secrete only a little lime in their tis- 

 sues, and have a more plant-like look. Even these grow so abundantly 

 on some coasts, that, when broken up and accumulated along the shore 



