Vol. 56.] SHALES OF THE WELSH BORDERLAND. 409 



species Cyrtograptus tubuliferus, while he regarded fig. 10 as the 

 type-form of Barrande's Monograptus Nilssoni. 



In the Riccarton (Wenlock) Beds of Southern Scotland occurs 



a graptolite, which agrees with 



.p. 91 -pv^ oo _ this type-specimen of M. Nilssoni, 



n [^' '7~ TVT^^n^Hn except in the matter of branching; 



Cvrtograptus Monograptu . K T ,, n . n & 



r \ ° i • AT-i n „: this is Lapworth s Ciirtoqraptus Car- 



Carruthersi. JNilssoni. . * «/ •' . r 



ruthersi. Jhrough the kindness or 



Prof. Lapworth I append here a 



figure of one of the type-specimens 



of his species, together with an 



example of M. Nilssoni. A similar 



form was collected by myself from 



the typical locality of Borek, in 



Bohemia, where C. Lundgreni, M. 



Nilssoni, and M. testis are found to 



occur on the same slab of rock. 



,_*^^ It will be evident that the two 



I forms M. Nilssoni and C. Carru- 



. -. thersi differ merely in regard to 



*■ ' ' '- 1 the matter of branching. This 



branching form, C. Carruthersi, is a Wenlock fossil, and is fairly 



characteristic of the highest beds of the Wenlock Shales, while 



M. Nilssoni is a typical form of the succeeding Lower Ludlow 



Beds. 



It may be frankly admitted that C. Carruthersi is in all proba- 

 bility the immediate ancestor of M. Nilssoni, if not identical with 

 it. But bearing in mind, on the one hand, that the branching 

 forms referred to Cyrtograptus are of the greatest importance as 

 Wenlock zonal indices, and on the other, that our knowledge of the 

 cause and meaning of the branching in the Monograptids is as yet 

 incomplete, it is not my purpose at present to suggest a change 

 in the accepted nomenclature. 



Cybtogeaptus mgidus, Tullb. (PI. XXIV, figs. 2 a, b, c, & 



text-fig. 23, p. 410). 



Tnllberg, ' Skanes Graptoliter ' pt. ii (1883) Sver. Geol. Undersokn. ser. C, no. 55, 

 p. 38 & pi. iv, figs. 12-14. 



Our British specimens do not agree exactly with Tullberg's 

 description, as there are many more thecse in the proximal part of 

 the rhabdosoma, but though Tullberg gives the number of proximal 

 thecae as six or seven, none of his figured specimens are complete. 

 They certainly show six or seven proximal cells, but there is no 

 sign of a sicula, nor is there any indication of the decided attenua- 

 tion which is commonly, indeed almost universally, characteristic 

 of this genus in the region of the sicula. I have noticed that it 

 is a common occurrence for specimens to be broken, leaving only 

 six or seven thecae below the branch, but am unable to account for 

 this. The thecse are inclined at an angle of about 20°, Tullberg^ 



