BRITISH GRAPTOLITES. 



Viplog. cometci). The distance apart of the cells is the same throughout, but the 

 shorter and thinner lower cells appear to be more distant, because they do not 

 overlap so much. In his drawings of Diplog. palmeus, Richter figures two aspects 

 of the polypary (" dorsal and ventral "), and shows that the medium septum is 

 incomplete. A similar structure is visible in his figures of Diplog. cometa. 



Another most important point first brought out by Richter in this paper is 

 that development among the Graptolites is in the direction of simplification of the 

 general forms. Thus the many-branched, forms of the earlier formations gave place 

 in the newer formations to those with two rows of cells, and these in their turn to 

 those with one row of overlapping cells, and eventually to those with free cells. 



Mode of Existence. — As regards their occurrence and mode of existence, Richter 

 appeared to be of the opinion that the Graptolites lived attached by the " foot " to 

 the floor of the ocean. Owing to their large size, they were probably not short- 

 lived, and they must have lived in enormous colonies to account for the numbers 

 found in the rocks. They are seldom found in association with other animals. 

 Richter observes that the forms with overlapping cells occur isolated, or in 

 association with other species, whereas the free-celled forms are found in groups 

 of their own kind. He suggests that this might be due to their greater or smaller 

 power of moving from place to place. All the Graptolites mentioned by Richter 

 in his paper occur in the Alum and Siliceous shales of Thi'iringia. 



The papers which appeared during the next few years are 

 of little importance, and are mainly stratigraphical in their 

 bearing. Fournet simply states that Graptolites occur in 

 limestones and shales associated with Gardiola interrupta, but 

 records no species. 



Fournet, 



" Sur les terrains- 



anciens de Neffiez, 



Languedoc," ' Bull, de 



la Soc. G-eol. do France,' 



ser. 2, vol. xi. 



1854. 



Beyrich, 



" Ueber das Vorkom- 



nini von Graptolithen 



im Schlesischen 



G-ebirge,"' ' Zeit. d. 



Deut. geol. Gesell.,' 



vol. vi. 



1854. 



M'Coy, 



' Description of tin' 



British Palaeozoic 



Fossil* iii the < !c<>- 

 logical Museum of 



< 'ainlirid^o.' 



Beyrich, in his paper " Ueber das Vorkommen von Grapto- 

 lithen im Schlesischen Gebirge," mentions no definite Grapto- 

 lite species. 



In his ' Description of the British Palaeozoic Fossils in the 

 Geological Museum of Cambridge,' M'Coy gives a description 

 of a few species of Graptolites, some of which also are 

 figured. Gr. convolutus, (1) Gr. latus, (2) Gr. lobiferus, Gr. 

 ludensis and var. minor (a new variety), (3) Gr. millepeda, 

 Gr. Murchisoni, Gr. Sagittarius, (4) Gr. Sedgwiclcii, (5) Gr. tenuis, 

 Diplog. foliaceus, D. folium, D. mucronatus, D. pristis, var. B., 

 1>. ramosus, (6) D. rectangularis, Diplogra/psus (?) sextans. 



