MONOGRAPTUS. 



483 



Figs. 338 c and d. — Monograptus Jim 

 briatus (Nicholson). 







Si 



^ ] 



- 





d 



it eventually be proved to be a character of specific 

 value, the form next described as a variety would 

 have to be regarded as a separate species. 



Affinities. — As respects the character of the 

 proximal end, Monog. fimbriatus approaches M. 

 triangulatus, but differs from it in the characters of 

 the distal thecse. It also resembles var. similis in 

 the form of the polypary and the characters of the 

 distal thecae, but differs in those of the proximal 

 portion of the polypary. 



Horizon and Localities. — Llandovery (base of 

 zone of M. gregarius, sub-zone of M. fimbriatus). 



8. Scotland: Dobb's Linn; Frenchland Burn ; 

 Garple Linn. Lake District : Skelgill. Ireland : 

 Wales: Rheidol Gorge, 420 and 430 yds. S.S.E. of 

 Bryn-chwith Farm, Pont Erwyd ; Llanystwmd wy. 



Associates, etc. — Monog. fimbriatus is one of the earliest of the Monograpti; it 

 occurs in S. Scotland immediately above the zone of M. cypMis, associated with 

 M. gregarius, M. rewlutus, M. railzhainiensis, Glypiog. tamariscus, Olimacog. Toru- 

 quisti, Petalog. palmeus var. latus, P. minor, etc. 



Collections. — British Museum (Natural History), Sedgwick Museum, Jones, 

 I jap worth, and the Authors, etc. 



c. Distal fragment, in relief, preserved 



so that apertural margins are con- 

 cealed. Same locality as fig. 338 b. 



d. Distal theca; showing reflexed aper- 



tural terminations. Ibid. 



Coalpit Bay, Donaghadee. 



Var. similis, var. nov. Plate XLVIII, figs. 5 a — d. 



1876. Monograptus convolutus var. fimbriatus, Lapworth, Greol. Mag. [2], vol. iii, p. 358, pi. xiii. 

 figs. 4 c, d. 



Fig. 339.- 



-Monograptus fimbriatus var. 

 similis, nov. 



In addition to the form just described, which appears to be the one designated 



originally as Monog. fimbriatus by Nicholson, there 

 is another closely allied to it which is commoner, 

 especially in beds of the same age in S. Scotland, 

 and which seems to deserve distinction as a 

 variety. 



In this var. similis the circinate portion of the 

 polypary is, as a rule, shorter than in the typical 

 form. The broader type of theca is developed at 

 once, and maintained throughout, while the thecas 

 themselves are more closely set, numbering eighteen 

 to fourteen in 10 mm. The sicula also is somewhat 

 shorter than in M. fimbriatus itself, measuring only *7 mm. in length. 



Proximal portion, showing sicula. 

 Dobb's Linn; Birkhill Shales. Sedg- 

 wick Museum. 



