Transactions. 53 



considerable length. The breadth of the adult portion of the 

 stipe from the solid axis to the cell mouth is from one to two 

 lines. The axis is capillary, the common canal is broad, some- 

 times attaining a width of ^th of an inch. The cellules are 

 long, slender, and pointed, their superior margins slightly convex, 

 and having a general direction at right angles to the axis ; their 

 inferior margin more extensively curved, the inner or I'asal por- 

 tion being sharply inclined to the axis, while the outer half is 

 nearly horizontal. Each cellule is of a triangular shape, the base 

 resting on the common canal, the cell apertures being at the 

 apex. The cellules are separate, from 20 to 24 in the inch, their 

 general inclination being slightly upwards, nearly at right angles 

 to the axis. Locality — Dobb's Linn, Garpel Glen, &c. 



Monograptus Sedgwickii, var. triangulatus. — This is a well 

 marked variety of M. Sedgioickii, and not a distinct species. Tlie 

 stipe is simple and moniprionidian, and is more or less curved, 

 beginning with a small radical and a slender curved proximal 

 portion, which gradually straightens as it reaches full develop- 

 ment. The axis is capillary ; the common canal is slender, and 

 very much narrower than in the normal form. The cellules are 

 from 20 to 30 in an inch, nearly at right angles to the axis, and 

 sometimes approaching the appearance of a Rastrite so nearly as. 

 to be mistaken for such. Locality— Dobb's Linn and Beld Crai"'. 



Monogrttptus fobi/ertis (M'Coy). — In this species the stipe is 

 linear, monoprionidian, often of great length. The full grown 

 individual reaches a breadth of one-tenth to one-twelfth of an 

 inch. The axis is slender. The common canal is rather broad and 

 well marked. Cellules are nearly at right angles with the axis, 

 but haAdng a slight upward inclination. Tiieir upper margin is 

 curved, terminating in obtusely rounded lobes, in which a notch 

 on the under side separates the rounded extremity from the 

 oblique descending margin (M'Coy). The cellules in full grown 

 specimens vary from 16 to 18 in the space of an inch. The base 

 is slender and curved, the common canal ha\ing a comparatively 

 greater width. The cell, as is occasionally well shewn, opens at 

 the notch in the under side of the cellule. Locality — Dobb's 

 Linn, Beld Craig, ifcc. 



Climacograptus teretiuscuhcs. — This genus was at first described 

 by Professor M'Coy, and named by him Dijdograptus rectangular is. 

 It is very abundant, having a wide range passing up through the 

 Skiddaw States, Lower and Upper Llandeilo, Caradoc, and Lower 



