IirSTORY OF RESEARCH. 



1868. 



Hall, 



' Introduction to the 



Study of the 



Graptolitidae," 



' Twentieth Annual 



Report of the State 



Cabinet.' 



through a perforated septum in the Ctenostomata, " distinguish them at once." 

 The various characters of the six groups of living Hydrozoa are given, but the 

 only two which he acknowledges have any affinities with the Graptolites arc 

 the Corynidse and the Sertularidae, and as there are no cells in the former, 

 Carruthers considers that the nearest allies of the Graptolites are the latter, 

 although they have no axis. 



As respects the mode of life of the Graptolites, Carruthers is inclined to the 

 opinion that they were attached, and points to the long proximal extension of the 

 radicle in G. scalaris as an example. He rejects Nicholson's idea of "floats" 

 and " swimming bells," and also his reproductive sacs and gonophores. 



The 20th Annual Report of the State Cabinet of New 

 York, published in the same year, contains a paper by Hall, 

 entitled " An Introduction to the Study of the Graptolitidae." 

 This is in the main a reprint of selections from his previous 

 memoir on the " Graptolites of the Quebec Group," but he 

 gives some "Supplementary Notes" on the genera Didy- 

 mograptus, Gladograptus, Dicranograptiis, and Goenograptus. 

 He points out that both M'Coy and Geinitz included under 

 each of the first two generic names two distinct types, and he suggests tin' 

 employment of Didymograptus (M'Coy) for such forms as l>. Murchv<oni, and 

 Cladograpsus (Geinitz) for forms of the type of l>. ramosus, etc., thus relinquishing 

 for the time his own genus Dicranograpfus in favour of the older title suggested 

 by Geinitz. As regards the Cladograpsus of Carruthers, Hall points out that there 

 is little doubt that it is similar to his own Gostiograptus, which may, again, be 

 identical with Emmon's Nemagraptus. 



Hall still asserts that it is generally impossible to distinguish between Didymo- 

 graptus, Tetragraptus, and Dichograpt us; but if the last of these names is to be 

 used, he suggests that it be restricted to such forms as Gr, SedguucJcii and Gr. aranea; 

 and he proposes the name Loganograptus for "those forms with central corneous 

 discs, while those which are repeatedly dichotomous, like Gr. fle.rilis, will constitute 

 a third genus." 



Hall also makes some additional remarks on Phyllograpfns, and on the presence 

 of a common body in this genus. 



In 1869 Heidenhain gave descriptions and some good 

 figures of a few species from the Graptolite-bearing boulders 

 of the Drift of Northern Germany. Descriptions only are 

 given of M. priodon, M. Sagittarius, M. colonus, and .1/. testis, 

 while there are figures of a new species— (1) .V. distans 

 (Heidenhain's species is identical with the subsequently 

 described M. scanicus, Tullb.), (2) .1/. IWsxoni, (3) .1/. 

 Salteri?, (4) .1/. Boh amicus, (5) M. Uoemevi (which, according 



1869. 



Heidenhain, 



" Ueber G-raptolithen- 



fiihrende Diluvial 



( reschiebe der Nord- 



deutschen Ebene," 



' Zeit. d.Deutsch. G-eol. 



GeselJ..,' Bd. xxi. 



