18 



p.u..t:ontoi.ogv of new-york. 



roSSII. I'LAMS OF THE CLINTON (.'ROl"?. 



It has been the practice to refci- to ve<i;elable origin all those fossil bodies of the older strafn, 

 which have, in their general aspect, their habit or mode of growth, some similarity 1o plants ; 

 and in which no organic structure can be detected, beyond, sometimes, the external markings. 

 These have been regarded as belonging to marine vegetation like the Fuci of the modern ocean, 

 and which from their nature coulij leave only impressions of their external form, or the outline 

 of this form replaced by stony matter. Tn this mode of treating the subject, it is not improbable 

 that some bodies wholly inorganic have been included under plants ; while others, likewise 

 included, may have been the polypidoms of some of the lower orders of zoophytes, such as 

 Alcyonidia, sponges or the like, which, requiring a small amount of calcareous matter, may 

 have lived in conditions where the calcareous zoophvtes could not have existed. In the present 

 state of our knowledge and means of determination, it is in fact impossible to decide to which 

 of these classes some of these bodies belong. We are not yet fully aware of the nature and 

 character of the fauna and flora of the j>eriod, nor of the impressions thev were capable of 

 leaving in the soft mud and sands forming the bed of the ocean in which they lived. In the 

 mean time, to neglect them altogether would be manifestly wTong ; since many of them are 

 conspicuous, and already well known ; and since it is only by attracting attention to the obscure 

 and unknown, that we can hope to learn its true nature. I have accordingly given figures of 

 such of these bodies as possessed peculiar characters, though not having positively determined 

 whether they belong to plants or zoophytes, and some even perhaps of inorganic origin. 



401. 6. BLTHOTREPHIS GRACILIS. 



PL. V. Fig. I a, b, c, d. 



J^coides gracilis. Report 4th Geol. Dist. New-York, 1843, pag. 69, Rg. 



Not B. gracilis, Pal. N. York, Vol. i, pag-. 6*2, pi. 21, fig. 1. The species of the Clinton grroup will 

 retain this name by precedence, and that of the Trenton limestone may be changed to B. tenuis. 



Plant slender, branching ; branches numerous, often crowded, irregularly diverging, some- 

 times with acute terminations ; entire plant slender and fragile. 



Tlie specimens of this plant, which may be fragments only of a larger one, present a main 

 or principal stipe, with numerous railiating and bifurcating branches which are often a second 

 time branched. Scarcely any two specimens are alike, and it is difficult to fix upon characters 

 which shall be decisive of specific distinction. This and the following species occur in the thin 

 fine-grained layers of shaly sandstone spread out on the surface of the thin Isminae. 



Fig. 1 a. A small delicate specimen of this species. The engraving represents the branches 



rather too slender and acute. 

 Fig. 1 l>. An elongated stipe with numerous branches. 

 Fig. 1 c. A fragment with several branches which are again subdivided. 

 Fig. 1 d. A large individual having fewer branches in proportion to its size, than the preceding, 



and approximating in character to the succeeding forms. 



. I 



