152 Mr. C. Lapworth on new British G.raptolites. 



4. Monograptus colonics, Barr. 

 (PI. IV. figs. 3 a-6 c, and figs. 4 a, 4 b.) 



Monograptus colomis, Barr. Graptolites de Boherne, pi. ii. figs. 1, 

 2, 3 ; Nicholson, Quart. Journ. Geol. Soc. vol. xxiv. pi. xx. figs. 9, 

 10, 11. 



In Plate IV. figs. 3 a-6 c I figure some examples of a 

 peculiar species of Graptolite, which is the only British form 

 known to me which distinctly approximates in its superficial 

 characteristics to the typical Monograptus colonus of Barrande 

 (Grapt. de Boheme, pi. ii. fig. 1). It agrees very closely 

 with some Bohemian forms referred to Barrande's species 

 examined by myself, but rarely exceeds the length given in 

 the specimens figured. The marginal spines appear to be 

 merely a mucronate extension of the apertural denticle, as in 

 the Dichograptidse. They are very distinct from the hori- 

 zontal thecal processes exhibited by such forms as Mono- 

 graptus leintwardinensis } &c. 



Barrande's young example (loc. cit. fig. 5) must belong to 

 a distinct species. It is not unlike the young form of M. 

 basilicus, Lapw., or, as I have elsewhere suggested *, may be 

 identical with Suess's Monograptus dubius. 



I know of no example of the present form, either British or 

 Bohemian, in which the virgula is not greatly prolonged dis- 

 tally. This invariable feature, together with the characteristics 

 of the closely-set hydrothecge, distinguish it at a glance from 

 all its congeners. 



Horizon and Locality. Not uncommon in the Lower Lud- 

 low beds of Vinnal and Leintwardine, Herefordshire. 



5. Monograptus galaensis, Lapw., var. basilicus } nov. 

 (PI. IV. figs. 6 a-6 d.) 



Monograptus colonus, Lapworth. Ann. & Mag. Nat. Hist. 1880, vol. v. 

 pp. 59, 60. 



Polypary stout and straight, several inches in length, 

 slowly augmenting in diameter to a maximum width of one 

 eighth of an inch. Hydrothecae sixteen to twenty to the inch, 

 inclined at an angle of about 45°, with convex proximal walls 

 overlapping each other for less than three fourths of their 

 length ; narrowing rapidly in the direction of the aperture, 

 the margin of which is concave, very oblique, and destitute 

 of ornamentation. 



The proximal portion of the polypary augments its dia- 

 meter very slowly, a length of several inches being attained 



* Lapworth, "Scottish Monograptidse," Geol. Mag. 1876, p. 506. 



