316 C. Lapicorth — 0)i Scottish Monograptidce. 



polypary ; and (2) tlie shape of the compressed hydrothecge, which 

 are triangular in form, with the apertural margin precisely normal to 

 the general line of the virgula. The polypary has consequently a 

 remarkably neat and compact appearance, leading to its immediate 

 identification. 



It somewhat resembles Monogr. intermedius, Carr. ; but in that 

 species the hydrothecge are arranged on the convex margin of the 

 polypary ; they are different also in their general form. Perhaps its 

 most intimate ally is Monocjraptus concinnus, Lapw., from which it 

 differs mainly in the size of the adult polypary, and in the details of 

 the hydrothecse. 



M. Barrande figures fragments of at least two distinct species 

 under this title (Grapt. deBoheme, plate 2, figs. 16-18). His largest 

 figure (fig. 16) is the only one to which his very full diagnosis can 

 be applied, and it holds good for the form here described. Fig. 17 

 of his plate is Monograptus gregarius, Lapw., and fig. 18 has 

 probably been taken from a 3'^oung example of some species of the 

 Sedgiuickii type. All palseontologists who have subsequently referred 

 to the species have very naturally fallen into similar errors. 

 Several distinct species of the Nilssoni group have been identified 

 with this typical form, which has itself never been refigured. 



The foregoing description has been drawn up from specimens in 

 the Cabinet of Professor H. A. Nicholson, collected by him in the 

 Lower Ludlow rocks of Leintwardine. 



Locality. — A few very doubtful fragments only have been procured 

 from the Birkhill Shales of Mountbenger ; and from the Gala beds of 

 Darnick, near Melrose. 



6. Monograptus intermedius, Carr. Plate X. Figs. 10 a — e. 



GraptolitJiiis intermedins, Carruthers ; Geol. Mag. 1868, Vol. Y- 



PI. V. Fig. 18. 

 Graptolites Nilssoni, Baily ; Characteristic Brit. Foss. plate ix. 



figs. 2a, h. 



Polypary from three to four inches in length, and with a maximum 

 diameter of one-twentieth of an inch ; distal portion broadly arcuate, 

 proximal portion normally strongly recurved. Hydrothecee, acut- 

 angular, 20 to 25 to the inch, adpressed to the periderm, in contact 

 only ; outer margin straight, apertural margin inclined. 



As a rule the proximal portion of the polypary in this species is 

 sharply recurved, and under this aspect it was originally figured and 

 described by Mr. Carruthers. It sometimes happens, however, that 

 this curvature is less pronounced, and there is a gentle and similar 

 curve throughout the whole length of the polypary. (Comp. Plate 

 X. Figs. 10 c, 6.) 



Fragments from the earlier extremity of the polypary are, except 

 for their peculiar dorsal curvature, almost inseparable from similar 

 fragments of 3L Nilssoni, Barr. In the adult portion the broad 

 triangular denticles are yerj characteristic. I am disposed to refer 

 the Graptolitlms acutus of Mr. Hopkinson to this species, fragments 

 of which from the neighbourhood of the proximal extremity often 



