468 MISS E. M. E- WOOD ON THE LOWER LUDLOW [May I9OO, 



make out all the characters, I went to Llanfair, and was fortunate 

 enough to find the locality from which Murchison had evidently 

 •collected his type-specimens. Moreover, in addition to those 

 which I myself collected, Dr. Humphreys, to whom my best thanks 

 are due, kindly lent me a very fine slab crowded with examples. 



All the Llanfair specimens are preserved in a hard calcareous 

 sandstone which weathers deeply, and it is only on this weathered 

 surface that the graptolites can be seen. Owing to this circum- 

 stance the apertures of the thecaa are generally imperfectly preserved, 

 especially near the proximal end, where the apertures are somewhat 

 turned underneath, and consequently half hidden from view. I 

 have been unable, therefore, to determine with certainty whether 

 the first thecse are spinose : that is to say, whether they are identical 

 in their characters with those of Barrande's Monograptus colours 

 or not. I believe that the first theca is spinose, but the succeeding 

 thecse are unprovided with spines. I have thought it best, therefore, 

 to separate M. ludensis from M. colonus as a distinct variety. It 

 agrees closely with M. colonus in general form and type of thecse, 

 but differs from it in the following particulars : — 



(1) The proximal three or four tbecse are not recurved ; 



(2) The adult thecae are fi instead of 4 times as long as wide; and 



(3) They overlap for a distance of more than one-half of their length. 



Even if it were proved that one of the species included under 

 Murchison's Gr. ludensis is identical with Barrande's Gr. colonus, I 

 think that it would not be advisable, even for the sake of priority 

 of nomenclature, to replace the well-known name of colonus by the 

 old and unfamiliar designation ludensis: one, too, which was given 

 with a most imperfect knowledge of the characters of the species, 

 and was published without a description and with an inadequate 

 drawing. 



L c a 1 i t y. — Llanfair (Montgomeryshire). 



Horizon. — Uncertain, but almost undoubtedly Lower Ludlow. 



Associat e. — M. dubius. 



¥ar. compactus nov. (PI. XXV, fig. 12.) 



This well-marked variety agrees with the typical M. colonus in 

 the shape of the thecse and character of the proximal extremity, 

 but is distinguished from it by the following characters : — 



(1) Polypary dorsally curved throughout, and never exceeding 25-4 cm. 



(1 inch) in length ; 



(2) Maximum width of polypary attained about the thirteenth theca, the 



width decreasing towards both extremities; 



(3) Virgula stout, and prolonged distally ; 



(4) There are forty -two to thirty-seven thecae in 1 inch (sixteen and a 



■half to fourteen and a half in 1 cm.) ; and 



(5) The proximal thecae are 3 times as long as wide, the adult 4^ times 



as long as wide. 



Only a few specimens of this form have been found, but the type 

 ■is in an excellent state of preservation. 



