504 J, Hopkinson — On New British Graptolites. 



in an inch, and their form is very different. G. tenuis (Portl.), if it be not merely a 

 variety of G. Nilssoni, is still further removed, its theca3 slightly overlapping one 

 another, and the entire polypary being not nearly so slender as in G. atlenuatus. 



Barrande figures,^ as a fragment of his G. proteus, a specimen which is most 

 probably referable to this species ; but as no description or enlarged figure is given, I 

 cannot be certain of their identity. 



Loc. Llandeilo : — Frenchland Burn, Moffat, Dumfriesshire ; Kirk Gill, Leadhills, 

 Lanarkshire. 



2. GraptolWhus acutus, sp. nov. — PI. XII., Fig. 4. 

 Polpary slender, slightly curved, and with isolated, acutely an- 

 gular hydrothecse, about 25 to the inch, rising from its convex 

 margin at an angle of about 30 degrees. 



The periderm of this little graptolite is almost as slender as that 

 of G. atteniiatus, not exceeding l-300th of an inch in breadth, but 

 the form of the hydrothecee is very different. The polypary is of 

 unknown length, the only specimens I have seen being on a single 

 piece of shale about an inch and a half square. The surface 

 of the shale, however, is covered with them, there being por- 

 tions of twenty or thirty individuals crossing it at all angles. The 

 curvature of the different specimens varies very much, some being 

 very nearly straight. The hydrothecse are barely isolated from each 

 other, the distal end of eachtheca reaching to, but never overlapping, 

 the proximal end of the next. Their outer margin, which is slightly 

 concave, forms an angle, with the axis, of about 20 degrees, and 

 their distal margin, constituting the aperture, forms an angle of 

 about 50 degrees with the axis, their apex being acutely angular or 

 sub-mucronate. The maximum breadth of the polypary, or the 

 distance between the apex of each theca and the dorsal margin of 

 the periderm, varies from about l-80th to l-50th of an inch. 



This species differs from G. intermednis (Carr.), the only form to which it bears any 

 resemblance, in the greater tenuity of the polypary, and in the form of the hydro- 

 thecfe, which are longer than those of G. intermedius in proportion to their breadth. 

 In the latter species, also, the thecse rise from the periderm at a greater angle than 

 in G. acutus. 



Loc. Llandeilo •.—GavT^le Linn, Moffat, Dumfriesshire. 



Family, DiPBiONiDiE. 



1. Diplograptus Etheridgii, Hopk. (Expl. Sh. 15, Geol. Surv. 

 Scotl.)— PL XII., Fig. 5. 



Polypary about an inch in length and l-30th of an inch in breadth 

 at its widest part, slightly contracted towards the proximal end, and 

 gradually decreasing in breadth towards the distal end; with a radicle 

 and lateral spines and a distally prolonged virgula. Hydrothecse 

 from 30 to 35 to the inch, forming but a slight angle with the axis, 

 slightly overlapping one another, and with a curved outline and 

 rounded apex. Apertures appearing as minute circular depressions 

 at the distal end of each hydrotheca. 



At the proximal end of the polypary two spines only are usually 

 seen, the central radicle being seldom perceptible. The polypary 

 almost immediately attains its maximum width, and then contracts, 

 for some distance almost imperceptibly, and then gradually more 

 rapidly, towards its distal end, the virgula, or so-called "solid axis," 

 being almost invariably prolonged beyond the other portions of the 

 1 Grapt. de Boheme. pi. iv., f. 3. 



