MONOGRAPTUS. 



473 



S. Scotland: Dobb's Linn ; Belcraig Burn. Lake District : Skelgill. Wales: 

 Llanystwmdwy ; Rheidol Gorge, 4o0 yds. S.S.E. of Bryn-chwith Farm, Pont Erwyd. 



Associates, etc. — Var. major occurs in the zone of M. gregarius, associated with 

 the zone fossil, M. communis, Glyptog. tamariscus, Climacog. Tomquisti, and Petalog. 

 palmeus var. latus. 



Collections. — Geological Survey of England and Wales, British Museum (Natural 

 History), Sedgwick Museum, Jones, Elles. 



Monograptus raitzhainiensis (Eisel). Plate XLVIII, figs. 3 a — c. 



1899. Monograptus triangularis var. Raitzhainiensis, Eisel, Ueber die Zonenfolge ostthiiring. u. 



vogtland G-raptolithenschiefer, p. 7. 

 1907. Monograptus triangulaius var. Raitzhainiensis, TGrnquist, Rastrites and allied species of 



Monograptus, Lund. Univ. Arsskr., n.s , afd. 2, iii, no. 5, p. 17, pi. iii, figs. 2 — 4. 



Polypary arcuate, with broadly circinate proximal portion, widening from 

 a very slender initial extremity to a maximum breadth of about 1'5 mm. 

 Theca? on the convex margin, twelve to nine in 10 mm. ; of two types, those 

 of the proximal portion of the general isolate Rastrites type, those of the 

 distal part in contact, apparently of the fimbriatus-triangulatus-communis 

 type, subtriangular, free fully four-fifths of length, with barb-like apertural 

 terminations, in which only one-fifth to one-third of the thecal length is 

 involved. 

 Description. — The appearance of the polypary is very striking, the difference in 

 the proximal and distal thecal being most obvious. 



The first fcheca is appressed to the sicula (which has a length of 1 mm.) for the 



greater part of its length, but the succeeding ones 

 Pigs. 329 a and 6.— Monograptus raitz- are li near an d isolate, this feature being characteristic 



lutuaensts (Eisel). ° 



of at least eight theca? ; then the adnate region 

 becomes broader and stouter like that of M. 

 triangularis, and finally the whole theca broadens 

 and resembles that of M. fimbriatus. The lower 

 wall, however, still retains traces of concave curva- 

 ture, and the theca? are really less blunt and more 

 widely separated from each other than in the true 

 M. fimbriatus, approaching M. communis in this 

 respect, but having longer theca? with less pro- 

 nounced reflexion of the apertural region. 



Affinities. — Monog. raitzhainiensis is in its way 

 unique, and if carefully examined can readily be distinguished from any of the 

 above-mentioned forms to which if bears a certain amount of resemblance. 



c S* 



a. Proximal portion. Enlargement of 



part of PI. XLVIII, fig. 3 a. 



b. Distal thecae. Enlargement of part 



of PI. XLVIII, fig. 3 c. 



