HISTORY OF RESEARCH. 



1851. 



Salter, 

 " Silurian Rocks of 

 Scotland," ' Quart. 

 Journ. Greol. Soc.,' 



vol. vii. 



1851. 



Prout, 



" Description of a New 



G-raptolite found in the 



Lower Silurian Rocks 



near the Falls of St. 



Croix River," ' Amer. 



Journ. of Science,' 



vol. ii, ser. 2. 



Iii the same year Salter, in an appendix to a paper by 

 Murchison on " The Silurian Rocks of Scotland," described 

 and figured two species of Graptolites, one of which was 

 new, from the Girvan district, viz. (1) Gr. tenuis and (2) 

 Viplog. bullatus. The figures, however, are not good, and it is 

 difficult, if not impossible, to identify the species. 



Two papers on Graptolites appeared in America during 

 this year. Prout described and figured a new form of Grap- 

 tolite under the name Gr. Hallianus. The drawings are poor, 

 and it is difficult to identify the Graptolite, but it clearly 

 belongs to the Dendroidea rather than to the Rhabdophora, 

 and is probably a Dendrogra/ptus. 



Prout also discusses the zoological affinities of the Grapto- 

 lites in some detail, and " with due deference to Beck " 

 thinks that this new species, and all those with a hollow central tube and tubular 

 cells, are allied rather to Sertularia than to Virgularia. For in the " Virgularia? 

 and Gorgonidas the tubes of the polypi have no regular connection with the 

 central axis, except through the medium of a fleshy or coriaceous envelope, and 

 it would be difficult to account for the tubular character of both the polyparium 

 and denticles of Graptolites, unless we suppose that the central or semi-calcareous 

 stem was entirely destroyed, while the fleshy envelope remained in a perfect state 

 of preservation, and this is extremely improbable." In other words, Prout 

 considers that the skeleton of Graptolites was external, as in the Sertularidse, 

 rather than internal, as in the Gorgonidge and Pennatulidae. In his new form 

 Gr. Hallianus, Prout recognises that there is no trace of a central axis, and 

 this being very indestructible when present, probably therefore never existed. 

 He believes that the "cup-like denticles" are "unilateral," "vaginated on their 

 external sides," and "inserted into a common connecting tube." Front considers 

 that probably both the " Sertularidae and Pennatulidae existed at the same time in 

 the ancient seas," and that some of the "differences of opinion on the origin of the 

 Graptolites may be found more seeming than real." 



The first edition of a general work by Geinitz ap- 

 peared in 1852, entitled " Die Graptolithen." It resembles 

 Barrande's memoir in its comprehensive character, but 

 Geinitz's views on the structure, development, and zoological 

 affinities of the Graptolites are little more than a repetition 

 of those formulated by Barrande himself. Indeed, the work 

 is critical and historical rut her than original or suggestive. 

 Geinitz differs from the vriewsof Barrande, Suess, and Boeck, 

 as to the direction of growth of the Graptolites, and con- 

 sequently as to the proper position for figuring them. lie 



1852. 



Geinitz, 



" Die Versteinerungen 



der Grauwacke- 



forination in Sacliseii 



uud den angrenzenden 



Lander Abtheilungen," 



Heft 1, ' Die Silurische 



Formation.' " Die 



Graptolithen." 



