458 



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



Fig. 11. — M. tumescens, 



Sp. 710V. (x5). 



MONOGRAPTUS TUMESCENS, sp. D.OV. (PL XXV, figS. 5 A & 5b.) 



Polypary from 2-5 to 3-8 cm. (1 to 1*5 inch) long, straight 

 for the distal four-fifths of its length, but the proximal one-fifth is 

 strongly incurved, making an angle of 10° or more with the general 

 direction of the polypary. Width at the aperture of the first theca 

 =about 76 mm. (-03 inch), increasing rapidly for the first three or 

 four thecae, at the rate of *38 mm. (-015 inch) for each theca, then 

 more gradually, the maximum width of 2 mm. (-08 inch) being 

 attained from the seventh to the tenth theca. From that point the 

 width decreases slightly, so that throughout the distal part the width 

 is only 1*77 mm. (-07 inch), thus giving the polypary a characteristic 

 form. The virguh, is so far as I have observed, not prolonged beyond 

 the distal extremity. 



Proximal Extremity. — Sicula 

 about 1*9 mm. (*075 inch) long and 

 •38 mm. (-015 inch) wide at the aper- 

 ture, hence it is 5 times as long as 

 wide. Aperture concave, somewhat con- 

 tracted, and provided with a long ventral 

 spine. Proximal extremity in other re- 

 spects similar to that of M. dicbius. 



Theca?. — Twenty-eight to twenty- 

 four in one inch (eleven to nine and a 

 half in 1 cm.), inclined to the axis at 

 an average angle of about 30° ; proximal 

 thecae less highly inclined than the 

 distal. All approximately similar in 

 form, being long and wide tubes with 

 straight or slightly concave apertures at 

 right angles to the direction of the 

 thecae, with an acute denticle, but devoid 

 of spines. Adult thecae about 2-54 mm. 

 (•1 inch) long, and 4 times as long as 

 wide ; the first theca is only about 

 3 times as long as wide. The adult 

 thecae overlap for from one-third to one- 



fa = Enlargement of proximal 

 extremity of fig. 5 a in 

 PI. XXV. 



b = Distal thecae of a spe- 

 cimen from Llettygyn- 

 fach.] 



half of their length. 



This form is one of the many which have been assigned to 

 M. colonus (Barr.). It will be evident, however, when the foregoing 

 characteristics are taken into consideration, that it is quite distinct 

 from all other species : its general form, and the disposition and 

 general characters of the thecae distinguishing it readily. In the 

 shape of the polypary it approaches somewhat closely to M. sub- 

 colonus, Perner, though it differs in the number and shape of the 

 thecae. It bears some resemblance to M. frequens, Jaekel, but the 

 identity of that species is doubtful. 



Localities. — Long Mountain (south side at Llettygynfach) ; 

 Montgomery Road ; Ludlow district (Elton Lane and Elton- 

 Ludlow Road). 



