C. Lapwortli — On Scottish Monograptidce. 499 



imaginary meltings. Such a theory has not yet, I believe, been con- 

 structed, nor can I, of course, attempt to do it. Is it not rather, 

 however, a question for the physicist than for the geologist ? It is 

 certain that glaciers do move, that they move in some respects like 

 rivers, that they have a great grinding power, and that they can be 

 driven up inclines ; but the physical details of the cause of the 

 motion, though in the highest degree interesting to the geologist, 

 are, I think, a little beyond his province to determine. 



lY. — N Scottish Monograptid^. 



By Charles Lap "worth, F. G. S. 



{^Continued from page 360.) 



(PLATE XX.) 



§ VII. 



Group 5. — Type, Monograptus lobiferus, M'Coy, sp. 



Folypary usually slender and curved. HydrotJiecce in contact only ; 

 distal extremity of each either rejiexed or coiled up into a rounded 

 lobe. 



26. Monograptus lobiferus, M'Coy, sp. Plate XX. Fig. 1. 



Graptolithus lobiferus, M'Coy ; British Palaeozoic Fossils, pi. i. b. 



fig. 3. Nicholson, Quart. Journ. Geol. Soc. vol. xxiv. pi. xix. 



fig. 30. 

 Graptolithus millepediay M'Coy; ibid., fig. 6. Geinitz, Die 



Graptolithen, Taf. iii. figs. 33, 34 ; Taf. iv. fig. 5. 

 Graptolithus Becki, Harkness ; Quart. Journ. Geol. Soc. vol. vii. 



pi. i. fig. 5. Geinitz, op. cit. Taf. iii. fig. 14. 

 Graptolithus Nicoli, Harkness ; Quart. Journ. Geol. Soc. vol. vii. 



pi. i. fig. 6. 

 Graptolithus priodon, Eichter ; Zeitschrift d. Deutsch. Gesellsch. 



1853, Taf. xii. fig. 22. 

 Diplograpsus nodosus, Harkness, loc. cit. figs. 10a — 106. 



Polypary slender, several inches in length, distal portion straight, 

 proximal portion sharply recurved. Hydrothecas 20 to 25 to the 

 inch, in contact at their bases only ; narrowing in the direction of 

 the apertural portion, which is curled up into a rounded lobe. 



The i)roximal or recurved portion of the polypary is compara- 

 tively short, rarely exceeding three-fourths of an inch in length. 

 Distally it is either perfectly straight, or has a very gentle dorsal 

 " curvature. The fully developed polypary must have been of extra- 

 ordinary length, as straight fragments of more than a foot in extent 

 are by no means rare. 



The hydrothecEe are subtriangular in form, and — exception being 

 made of their peculiar terminal curvature — they agree precisely in 

 their form and disposition with those of Monograptus convoliitus, His. 

 They rise perpendicularly from the convex margin of the periderm, 

 and their bases, which just touch each other at their extremities, 

 have a length which is the same as, or but slightly less than, that 



