42 BULLETIN 65, UNITED STATES NATIONAL MUSEUM. 



Genus ODONTOCAULIS Lapworth. 



Odontocaulin Lapworth, Quart. Journ. (Jeol. Soc. London, XXXVII, 1881, 

 p. 175.— PocTA, Syst. Sil. Centre Boheme, VIII, Pt. 1, 1894, p. 171.— 

 RuEDEMANN, New York State Mus., Mem. 11, IDOS, p. 172. 



Doctor Gurley remarks on Odontocanlh as follows: 



This genus was thus establisLed by Lapworth for forms which virtually com- 

 bined two characters: (1) Absence of disscpinients, and (2) a polypiferous 

 stem. Its only distinction from Dicttjoiunifi and CuUograptus lay in these two 

 features. But in (). occidcntalis we tind dissepiments aloiiy icitli the polypifer- 

 ous stem. Whence there is now no generic distinction whatever between these 

 two Odontocaitlis species and the CaUograptus species at the same horizon, 

 except the single one of the thecje on the stem. But it is not at all improbable 

 that this is merely a question of better preservation, well-preserved stems being 

 thecate. At least, of the two specimens of O. occidcnialiH, both showing the 

 stem, one shows thecje perfectly, the other only very obscurely. 



Having said this, however, a contingency may properly be noted. May it 

 be possible that aU the Callograpti at this horizon have thecate stems (in 

 other words, all be referable to Odontocanlis) ? There is. I think, some ground 

 for such a surmise. As Holm has said for Dicti/oncnia, so now for ('(lUograp- 

 iiis, the very great geologic range of the genus is a reason for suspecting the 

 valitlity of the generie reference of the species. May it not then be possible 

 that, compelled as we are for the most part to deal with and to base our 

 species upon fragments of the meshwork, we are confounding two series ; say, 

 for illustration," a series lower Ordovician (Calciferous) in distribution, and 

 a series upper Silurian (Niagara) in distribution, Itoth seines agreeing in type 

 of meshwork (probably a character of subordinate biologic value), but diffei'- 

 ing in characters of the base. At present there is nothing to negative such a 

 view. Until we know the proximal portion of the type species (C nalteri) this 

 reasoning must, of course, remain purely a possibility. But in a review like 

 the present a clear outlining of future possibilities may be justifiable. Cer- 

 tainly only under some such condition, it seems to me, would Odoiiloraidis 

 stand much chance of ultimate retention. Its provisional retention I think 

 advisable, pending a fuller knowledge of the condition of the base in the 

 remaining Xiagai'a CaUograptus species. At present its most distinctive char- 

 acters seem to be : Polypary arising from a single stem, lohieh is expanded 

 proximaUy into a ''disk," and is thecaphorons along one side; distal hnineJirs 

 more or less connected by dissepiments. 



Genotype. — Odontocaulis keepingi'Lii\\)\\o\{\\. Llandovery, of Devils 

 Bridge, Aberystwyth, Cardiganshire. 



ODONTOCAULIS GRANTI (Spencer). 



Callograplus granti Spencer, Canadian Nat., X. 1882, p. 10.". nnmrn nudum: 

 Trans. Acad. Sci. St. Louis. IV. 1884. pp. 564, 571, 572. i)l. 1. fig. 10: 

 Bull. Mus. Univ. State Missouri. I, 1884. pp. 14. 21. 22. pi. 1. fig. 10.— 

 Gurley, Journ. Ceol.. IV. 1896. pp. 93. 308, 



The original descrij^tion is as follows: 



Frond originating from a single stipe; branches slender, and bifurcating 

 two. three, or four times, and principally (niginating near the connnon radicle. 



" For illustration only, and as a pure surmise of the possibilities of the case. — 

 R. K. Gurley. 



