356 C. Lajnvorth — On Scottish Monograptidce, 



M. Riccartonensis differs from M. JTalli merely in the curvature of 

 the polypary, and in the form and inclination of the apertural spine. 



Locality. — Everywhere in the Riccarton beds ; at Kiccarton, Hind- 

 hope, Edgerston, Balmae, Dalton, etc. 



20. MoNOGRAPTus Galaensis, sp. nov. Plate XII. Figs. 5 a — d. 

 Polypary five or six inches in length, straight or very slightly 



curved, and with a maximum diameter of one-twelfth of an inch. 

 Hydrothecse inclined at an angle of about 30°, 24 to the inch, over- 

 lapping each other for less than one-third of their length ; slightly 

 contracting in diameter towards the aperture, the margin of which is 

 oblique, and forms a blunt triangular denticle. 



The proximal portion of the polypary is comparatively long — the 

 maximum diameter being rarely attained within the first three inches 

 of its length. The extremity itself is blunt, and the sicula is similar 

 in form to that of M. priodon, Bronn., but is of much smaller size. 

 The hydrothecie present appearances which differ according to their 

 position and to the direction in which compression has been effected. In 

 the adult portion of the polypary they are stout tubes, a little flattened 

 transversely, and gradually contracting distally. The plane of the 

 aperture is oblique with respect to the general line of the ventral 

 margin, with which it makes an angle of about 120°. The denticle, 

 though short and triangular, is very conspicuous. It sometimes bears 

 a short spine, which lies in the same plane as the edge of the aperture. 

 Near the proximal extremity the hydrothecse are narrower, and there 

 is a long acuminate denticle, generally strongly reverted. In some 

 views the hydrothecge appear to expand in the direction of the 

 aperture, and the ventral margin is not unlike that in M. Sisingeri, 

 Carr. 



The polypary in this form seems to have been much thinner in 

 texture than that of M. priodon, with which it is most frequently 

 associated. It is always preserved as a mere carbonaceous film, often 

 side by side with examples of the latter species in full relief. 



In the profile view this species is at once distinguished from all 

 other forms of the group,- the ventral margin appearing as a direct 

 line, along which project the minute triangular denticles at regular 

 and distant intervals. It has been hitherto confounded with M. 

 colonus, Barr. 



Locality. — Gala Group in abundance, at Buckholm, Darnick, 

 Glendearg, Wooplaw, Tushielaw, etc. 



21. MoNOGEAPTUs PRIODON, Bronn. 



Lomatoceras priodon, Bronn. ; Lethea Geogn., plate i. fig. 13. 

 Graptolithus Yel Graptolites priodon, Barrande; Grapt.de Boheme, 

 plate i. figs. 1 — 14. Geinitz, Die Graptolithen, plate iii. figs. 

 20 to 27, 29, 32, 34. Nicholson, Quart. Journal Geol. Soc. 

 vol. xxiv. plate xx. figs. 6, 7. 

 This well-known species has often been correctly figured and 

 described. It differs from all the remaining forms of this group in 

 the shape of the distal portions of the hydrothec^, which are so re- 

 curved that the apertures face the proximal extremity of the poly- 



