HISTORY OF RESEARCH. xxix 



jg52 Bronn, in the 1851 edition of his ' Letlmea Greognostica,' 



Bronn, enumerates twenty-seven species of Graptolites belonging to 



' Lethaea Geognostica,' the genus Graptolithus, of which he asserts that twelve are 

 • l " of Lower Silurian and fourteen of Upper Silurian age, while 



he records one species from the Bergkalk (Mountain Limestone). He gives figures 

 of (1) Gr. priodon, (2) Rastrites IAnnmi, and (3) Betiolites Geinitzianus, but these 

 are all copied from Barrande. 



J852 During the same year that witnessed the appearance of 



Boech, Scharenberg's work (1851), a paper was published by Boeck, 



' Bemaerkninger anga- an author who, unlike Scharenberg, was not acquainted with 

 aonde Graptolitherne.' Barrande's memoir. The illustrations of this paper are 

 excellent, but the conclusions drawn from them are characterised by the same 

 timidity of interpretation as that noticed in Scharenberg's paper; and, like many 

 other writers at that time, Boeck attributed several characters, now known to be of 

 specific value, to accidental deformation. 



Classification. — This part of his paper is of little value. He considers that the 

 Prionotus scalar is of Hisinger is the same as D. pristis ; but none of the specimens 

 figured by Boeck under these names are referable to either of these species as 

 now defined. One of his forms, however, is easily identifiable from the excellent 

 illustrations with Climacog. Scharenbergi, Lapw. (fig. 10). Under the title Pr. sutjit- 

 tarius he figures fragments of a form which may be a species of Didymograptus. 

 Boeck's Pr. folium (fig. 27), which he considers to be identical with Gr. foliaceus, 

 is possibly a Phyllograptus. Gr. Murchisoni (fig. 24) (or var. gerninus) is 

 well figured, but Boeck regards the branching in this species as an accidental 

 structure, the result of splitting. One of the figures (fig. 80), which is supposed 

 to represent Gr. Murchisoni, is apparently the species subsequently named by 

 Lapworth Bryograptus Kjerulfi. Boeck considers that Schlotheim's OrtJioc. 

 serratus is identical with the Pr. sca.laris of Hisinger. 



Structure. — The structural features of the Graptolites are most carefully 

 described and named by Boeck in this paper, though the connection and functions 

 of these structures can hardly be said to have been fully realised by him. He con- 

 siders that the skin or test of the Graptolite was partly elastic (or rather con- 

 tractile). This test formed a kind of tube, which was prolonged into a narrow, 

 pointed part — apex. The varying length of this apex was due to the fact that it 

 was attached to an internal contractile organ, which could draw the apex back into 

 the tube. The longitudinal dorsal groove (" suture " of Nicholson) lie terms the 

 sulcus longitudinalis, and this might be either straight, undulate, or angulate. The 

 curious transverse grooves running from the angles from this sulcus in C. Scha/renbergi 

 he terms sulci laterales, while the grooves formed by the cell apertures themselves 

 are named sulci transver sales. The edges of these sulci (or costae) are con- 

 sidered by him to be thickenings of the skin of the tube, and this thickening 



