488 Nicholson — On Spore-cases of Graptolites. 



m.— On some Fossils from the Graptolitic Shales of 



DUMFEIESSHIBE.^ 



By Henry Alleyne Nicholson, B.Sc. ' 

 (PLATE XVII.) 



THE Upper Llandeilo Eocks of the South of Scotland have long 

 been known to yield graptolites in great profusion, few other 

 forms of animal life being recognised as occurring in them. Having, 

 this summer, had an opportunity of examiaing the graptolite-shales 

 of Garple Linn, near Moffat, I was struck with the occurrence in 

 them of numerous bodies, differing from the graptolites in form, 

 though resembling them in mineral texture. 



These bodies present themselves as glistening pyritous stains, 

 scattered in considerable numbers among the graptolites upon the 

 surface of the shale. In their most perfect condition (Plate XVII. 

 Fig. 1, 2) they appear to be bell-shaped bodies, averaging Ihree- 

 tenths of an inch in length, and two-tenths in breadth, and pro- 

 vided at one extremity with a prominent spine or mucro, the other 

 terminating in a gently curved or nearly straight margin. When 

 compressed from above downwards, a condition in which they not 

 seldom occur (Fig. 4, 5), they appear as oval, or rounded patches, 

 often very definite in their outline, and presenting somewhere within 

 their mai'gin an elevated point, suirounded by several concentric, 

 elliptical, or circular rings, disposed with more or less regularity. 

 The elevated point marks the position of the mucro, and the con- 

 centric ridges are merely due to vertical compression. In this state 

 they are not unlike orbicular brachiopods in appearance. 



The texture of these bodies appears to have been corneous, like 

 that of the graptolites themselves, but they show no traces of struc- 

 ture beyond the presence of the mucro, from which, in some well- 

 preserved specimens, a filiform border is prolonged along the free 

 margin of the body. The mucro appears to have constituted the 

 most solid portion, standing up as a marked elevation, when ob- 

 tained in relief, and leaving an evident hollow in the cast. In 

 most cases these bodies are free and independent, but they occa- 

 sionally occur in such close juxtaposition with the stipe of a grap- 

 tolite, as to justify the belief that the connexion was organic and 

 not simply accidental. The only case in which I have observed this 

 is in Graptolites SedgivicTcii (Fig. 3, 3 a), the form in which it might 

 most reasonably be expected, as the cellules are separated from one 

 another by a conspicuous interval till close to their bases. In this 

 case the body appears to spring from the common canal, or coenosarc, 

 of the graptolite, and the mucro appears to have been situated at the 

 free extremity, and therefore to have constituted a point of dehis- 

 cence rather than one of attachment. 



The occurrence of these bodies in shales crowded with graptolites 

 and graptolitic germs, and their close connexion in some cases with 

 the graptolites themselves, would seem to warrant the conclusion 



* Eead before Section C. British Association, Nottingham. 



