C. Lainoortli — On Scottish Monograptidce. 501 



united to each other by their lateral faces, and are so similar in their 

 external features that it is impossible to say which was the funda- 

 mental germ. These monstrosities occur in association with forms 

 in which the sicula throws off a single series only. Figures illus- 

 trative of this remarkable deviation from the normal mode of develop- 

 ment (which occasionally occurs also in M. runcinatus and J/, tenuis) 

 are given on Plate XX. 



The typical example of this species figured by Barrande is the 

 Gala form mentioned above, in which the proximal extremity has 

 a slight double curvature. 



Locality. — Common in the highest beds of the Birkhill Shales at 

 Birkhill, March Burn, Eldinhope^ Eiver Ettrick, etc. ; and in the 

 Gala Group at Meigle, Cascade, Caddonfoot. 



28. MoNOGRAPTUS Clingani, Carr., sp. Plate XX. Fig. 3. 

 Graptolitlius lobiferus, Nicholson ; Quart. Journ. Geol. Soc. vol. 



xxiv. plate xis. fig. 29. 

 GraptoUthus Clingani, Carruthers ; Geol. Mag. Vol. Y. Plate Y. 

 Fig. 19. 



Polypary long and narrow, distal portion almost straight; proximal 

 extremity recurved. Hydrothecae 25 to 30 to the inch, in contact at 

 their base only, subtriangular in form, contracting in the direction 

 of the aperture, which is bent round so as to face the proximal ex- 

 tremity of the polypary. 



The hydrothecae are similar in form along the whole of the length 

 of the polypary. Each is a minute triangle, of which the base is 

 almost equal to the height. The distal portion is prolonged, and the 

 external orifice is comparatively narrow. The former is bent back- 

 wards at right angles to the axis of the theca, and the latter opens in 

 the direction of the proximal extremity of the polypary, parallel 

 with the general line of its polypiferous margin. 



Young examples occur in great abundance, and it was upon these 

 that the species was founded. The adult form is rare, and has only 

 recently been distinctly identified. 



M. Clingani is a very unsatisfactory species. It may best be 

 regarded as lying between M. convolutus (communis) and M. lobiferus. 

 From the former it is separated by the abrupt reflexion of the terminal 

 portion of its hydrothecas, and from the latter by the absence of a 

 distinct rounded lobe. 



Locality. — Common in a single zone in the higher portion of the 

 Birkhill Shales at Dobbs Linn, Moory Syke, Whitehope Burn, etc. 



29. MoNOGRAPTUS RUNCINATUS, sp. nov. Plate XX. Fig. 4. 

 Polypary several inches in length, narrow and gently curved 



throughout. HydrothecEe 24 to 28 to the inch, narrow tubes ex- 

 panding slightly in the direction of the aperture ; proximal half of 

 each appressed to the concave margin of the periderm, distal portion 

 free and abruptly reflexed, the aperture being directed obliquely 

 inwards ; denticle acuminate, conspicuous. 



The form of the polypary is very similar to that of Monograptus 

 BecTci, and the early hydrothecee in both species are almost identical. 



