Lapworth — GraptoliTes of Co. Down. 127 
been almost wholly derived from the equivalent black shales of the Moffat 
series. Several of these have already been figured by myself in the “ Cata- 
logue of the Western Scottish Fossils,” issued under the auspices of the British 
Association (Glasgow, 1876). 
To such species or varieties as are yet undescribed a brief diagnosis is here 
appended. 
Genus I. Rastrites, Barrande. (Grapt. de Boheme. PI. 4 -) 
According to Herr Richter, the thecae in this genus are mere orifices in the 
periderm of the common canal, and the long isolated and perpendicular tubes 
are simply ornamental or defensive extensions of the test. (1.) The British 
specimens which have hitherto come under my notice have afforded no support 
whatever to this opinion. 
Mr. W. Carruthers figures a magnificent example of Monograptus spiralis 
(Geinitz), (2) of which a well-marked example of Rastrites peregrinus (Barr.) 
seems to form the initial portion, and to be organically connected with it. I 
have recently examined the specimens from which the figure was taken, and I 
am inclined to believe that this appearance is owing to the accidental juxta- 
position of the two forms. 
1. Sp. 1. Rastrites peregrinus. Barr, Plate 5 > fig* I* 
The typical form of this well-known species is abundant in the dark shales 
of Coalpit Bay, a locality which has yielded the only specimens known to me 
in which the virgula is apparent as a distinct structure. (3). Locality — Coalpit 
Bay. 
2. Var. hybridus. Lapw. Plate 5, fig. 2. 
This variety is possibly identical with the fragmentary form Rastrites fugax 
of Barrande. (Grapt. de Boheme. PI. 4. ) Locality — Coalpit Bay. 
Genus II. Monograptus, Geinitz. Restricted. (Die Graptolithen, p. 32.) 
3. Sp. 1. Monograptus triangulatus . Hark. PI. 5? fig* * 4 * Locality — Coal- 
pit Bay and Tullygarvan. 
(1.) Richter. Aus die Thuringe Gebirge, Zeit. der Deutsch Gesellschaft, 1871. 
(2.) Carruthers. Geological Magazine, 1868. PL 5, fig. 1. 
(3.) Geological Magazine, 1876. PI. 10, fig. 1. 
