C. Lapworth — On Scottish Monograptidce. 359 



Polypary bent into an irregular spiral, and with an extremely 

 slender proximal portion bearing distant, adnate, linear hydrothecaj 

 with everted denticles. 



The distal hydrothecas in this variety are longer than in var. com- 

 munis, and much broader at their outer extremities than those in the 

 following variety. Their apices are often a little recurved. The 

 proximal portion of the polypary affords the chief characteristic of 

 this variety. It is as slender as many of those of the Nilssoni group, 

 and bears similar adnate hydrothecas. 



Locality. — In the highest beds of the Birkhill Shales at Duff kinnel, 

 Mountbenger, etc., and in the Gala Group at Grieston, Broad- 

 meadows. 



Yar. (d.) spiralis, Geinitz. Plate XIII. Figs. 4 g, h. 



Graptolithus spiralis, Geinitz; Neu. Jahrbuch fiir Mineral., 1842, 



pi. X. Barrande, Grapt. de Boheme, pi. iii. figs. 10, 11, 12. 



Nicholson, Quart. Journ. Geol. Soc. vol. xxiv. pi. xx. fig. 28. 



Polypary long and slender, coiled up into aflat spiral, and bearing 



long linear acutely-pointed hydrothecse. 



The thecce in this form ar'e very similar in shape to those of the 

 next species, to which it seems most intimately allied. 



Locality. — Rare in the higher zones of Birkhill Shales at Duff- 

 kinnel, Sundhope, Dobbs Linn. 



24. MoNOGRAPTUS TRIANGULATUS, Harkncss sp. Plate XIII. Fig. 5. 

 Bastrites triangidatus, Harkness; Quart. Journ. Geol. Soc. 



vol. vii. plate i. fig. 3 d. 



Polypary rigid, slender, from one to two inches in length, arcuate 

 distally, and with broadly incurved proximal portion. Hydrothecas 

 rising almost perpendicularly from the convex margin of the polypary, 

 25 to 28 to the inch, isolated, or in contact only ; narrow, linear, with 

 mucronate extremity and terminal aperture. 



I have separated this form as a distinct species, because of the 

 diminutive size and very characteristic shape of the polypary. It 

 occurs in great multitudes in one zone of the Birkhill Shales, and 

 always with the same general aspect. 



The hydrothecse are very similar to those of var. spiralis, Geinitz, 

 but they are narrower at their bases and more deeply divided. Near 

 the proximal extremity of the polypary they are distinctly isolated, 

 and greatly resemble those of some forms of Bastrites. Distally 

 their bases grow broader, and they appear to be truly in contact. 

 This is not always the case, however, for in some specimens all the 

 thecae seem to be really isolated, as in Bastrites. 



Locality. — Birkhill Shales, at Dobbs Linn, Garple, Glenkiln, 

 Frenchland, etc. Gala Group at Sit Burn, Heriot Water, etc. 



25. MoNOGRAPTUs TURRicuLATDs, Barrande. Plate XIII, Fig. 6. 



Graptolithus turriculatus, Barrande ; Grapt. de Boheme, plate iv. 

 figs. 7 — 11. Nicholson, Quart. Journ. Geol. Soc. vol. xxiv. 

 plate XX. figs. 29, 30. 

 Polypary slender, three to four inches in length, enrolled in a 



