456 



MISS E. M. K. WOOD ON THE LOWER LUDLOW [May I906, 



sicula prolonged as a coarse curved spine about 5 mm. (-02 inch) 

 in length. The first theca, 1 mm. (-04 inch) long, arises distinctly 



above the aperture of the sicula, being 



Pig. 10. — M. vulgaris, inclined to it at an angle of about 30°. 



s-p. nov.from Trefnant- The sicula extends to the level of the 



Middletown Brook, lower edge of the aperture of the second 



Long Mountain. ( X 5.) theca. 



T h e c se . — T wen ty-eigh t to twenty - 

 four in the inch (eleven to nine in 

 1 cm.), inclined to the axis at angles 

 of 35° to 40°. They vary considerably 

 in shape according to the manner of 

 preservation, but appear to be midway 

 between those of M. dubius and M. 

 colonics. The more proximal thecae are 

 short and wide tubes not quite twice 

 as long as wide, with widened apertures 

 of the typical M.-dubius type. Adult 

 thecae considerably longer, measuring 

 2-75 mm. ('11 inch), and 4 times as 

 long as wide. Increase of length and 

 relative decrease of width of the thecse 

 very gradual. Amount of overlap nearly 

 one half (in the distal thecse). 

 Affinities. — M. vulgaris may be readily distinguished by 



[« 



Proximal extremity, with 

 sicula. 

 b = Distal thecae.l 



(a) Its comparatively large size ; 



(b) The general shape of the polypary ; 



(c) The character of the proximal end ; and 



(d) The character of the thecas. 



The only species to which it is allied and with which it might be 

 confused is M. largus, Perner. It is somewhat difficult to deter- 

 mine correctly the characters of this Bohemian species, as the figures 

 are not quite in agreement with Dr. Perner's brief description. Thus 

 he states the width at the proximal end to be 1*7 mm., whereas 

 the width, as measured from his fig. 23 (op. cit. pi. xiv), is -85 mm., 

 and none of his figures show a width exceeding 2*8 mm. (5 mm. in 

 description). The Bohemian species appears, however, to be con- 

 siderably larger than the English form. Again, the polypary is said 

 to be straight, except at the proximal end, which shows a greater 

 incurve than do the English specimens, and the adult thecae are 

 relatively shorter and broader. Dr. Perner, unfortunately, does not 

 figure the sicula complete, which would enable one to determine the 

 identity or otherwise of these two forms. M. vulgaris approximates 

 closely to the form figured by Dr. Perner (op. cit. pi. xvii, fig. 17), 

 and provisionally referred to M. dubius, in general form and shape. 

 The sicula also appears to be somewhat similar, but there are only 

 twenty or nineteen thecse in the inch as against twenty-eight to 

 twenty-four (eleven to nine in 1 cm.). It is easily distinguishable 

 from all other English forms. 



