C. Lapivorth — On Scottish Monograptidce. 545 



The hydrothecse are of the type of those of Honograptus Nilssoni, 

 BaiT. They are very widely set and just touch each other at 

 their extremities. Each is of the general form of an inverted cone, 

 and is pressed flat against the margin of the periderm. The outer 

 edge of each is straight and makes an angle of about 30 degrees 

 with the axis of the branch. The apertural margin is usually much 

 inclined, so that the denticle is distinctly acute. It is occasionally 

 prolonged in a slender spine. 



Fragments of Cyi-tograptus Carruthersi are easily distinguished, 

 from those of Mbnogr. Nilssoni, which occurs upon the same horizon, 

 by the size, shape, and number of the hydrothecse. 



I dedicate this striking form to Mr. Wm. Carruthers, F.E.S., the 

 founder of the genus, to whom I am greatly indebted for assistance 

 in my work among the Graptolites. 



Locality. — Kiccarton Beds of Elliotsfield, Shankend, Eiccarton, 

 Mosspaul. 



36. Cyrtograptus Grayi, sp. nov. Plate XX. Figs. 11 a, 11 h} 



Polypary unilateral, monoprionidian : branching and re-branching. 

 Branches slender, flexuous. distant. Hydrothecse 20 to the inch ; 

 slender tubes, the earlier portion of each closely adpressed to the 

 periderm ; distal portion isolated and partly coiled up into a rounded 

 lobe. 



Although fragmentary examples occur in abundance in one locality 

 in the Girvan district, our knowledge of this species is yet far from 

 being complete. I figure the most perfect specimen hitherto detected 

 (Plate XX. 11a). The principal branch is short, much curved 

 and of great tenuity. The secondary and tertiary branches are long 

 and flexuous. Their diameter, including that of the hydrotheca3, 

 never exceeds one-thirtieth of an inch. The latter are of the type of 

 those of Ilonogr. lohiferus, M'Coy ; and, as in many of the species 

 of the group tj'pified by that form, the free lobed portion increases 

 in extent as the polypary grows in length. In the earlier portion of 

 the primary branch the free portion is scarcely perceptible ; while 

 in the better developed portions of the tertiary branches at least 

 half the theca is isolated and the lobe is rounded and very con- 

 spicuous. 



This species is named after its discoverer, Mrs. W. Gray, whose 

 unequalled collection from the Silurian rocks of Girvan has already 

 been of such signal service to science. 



Locality. — Girvan beds, Ayrshire, at Penwhapple Glen; Gala 

 Group at Yair, Elwand ? 



§ IX. 



DiMORPHOGRAPTUS, gCU. nOV. 



Gen. Char. — Polypary originating from a persistent adherent siciila ; 



proximal portion monoprionidian ; distal portion diprionidian. 



Pending the complete elucidation of their structure and affinities, 



I propose to unite provisionally under the foregoing title some 



very remarkable fossils of rare occurrence in our Scottish rocks, 



1 See Geol. Mag. for Nov. p. 507. 



DECADB II. — VOL. III. — NO. XII. 35 



