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



allied to Monogrcvptus colonus, but on examination it presents so many 

 differences that I am of opinion that it should be regarded as a 

 distinct species rather than merely as a variety of that form. It 

 differs from M. colonus in the following particulars : — 



(1) The polypary is shorter and narrower ; 



(2) Width of the polypary increasing more uniformly throughout ; 



(3) Distal prolongation of the virgula more persistent and conspicuous ; 



(4) The thecas present a smaller amount of overlap ; and 



(5) The excavation at the base of the free part of the theca is peculiar. 



It agrees with M. colonus in general form, and in possessing two 

 types of thecae ; and it occurs in abundance at the same horizon 

 as that at which one would expect to find M. colonus in the Long 

 Mountain district. 



M. varians is remarkable in presenting certain variations even in 

 the same limited area, and, so far as can be judged, at the same 

 horizon. It occurs at several localities in large numbers, in association 

 with M. Nilssoni, on the north side of the Long Mountain; at the 

 easternmost locality, namely at Wilmington Green, it is usually only 

 12-7 to 19 mm. (*5 to *75 inch) long, and the first two thecae are 

 spinose. At the Old Dingle Mill, lj miles farther west, it occurs 

 also in great abundance in association with M. Nilssoni, but is 

 longer, and the first theca alone is spinose. Some 2| miles 

 still farther west, above Garbett's Hall, it is still long, but has 

 the first two thecae spinose. These variations are quite constant 

 for each locality. Between Winnington Green and Old Dingle Mill 

 in the Trefnant-Middletown Brook M. varians occurs in association 

 with Betiolites spinosus and M. Nilssoni, but is broader and coarser- 

 looking, and the first three thecae possess strong spines. As already 

 mentioned in the first part of this paper, it is uncertain whether 

 these graptolites occur here at a higher horizon than usual. The fore- 

 going facts are interesting, as showing how readily small variations 

 may take place even within so limited an area. 



Var. a nov. (PI. XXV, figs. 16 a & 16 b.) 



1880. Monograptus colonus (Barr.) Lapworth, Ann. & Mag. Nat. Hist. ser. 5, 

 vol. v, p. 152 & pi. iv, figs. 3 b-3 d. 



This form was figured by Prof. Lapworth from a specimen found at 

 Mary Knoll, Ludlow, and belonging to Mr. Hopkinson, as M. colonus 

 (Barr.). Other examples have been collected by me from Stormer 

 Hall, and I regard it as a variety of M. varians. It resembles 

 the typical M. varians in 



(1) The form of the thecae ; 



(2) The long distally-produced virgula; and 



(3) The character of the proximal extremity. 

 It differs from it in : — 



(1) Its greater width of 2*1 mm. (*08 inch), which is attained more rapidly 



in M. varians ; 



(2) Its higher angle of inclination of the thecae, namely 40°; and 



(3) The greater number of thecas in the inch (thirty-five to twenty-eight). 



Horizon. — Zone of M. Nilssoni. 



Associates. — M. Nilssoni, M. chimcera var. Salweyi, and 

 M. dubius. 



