Mr. C. Lap worth on neio British Graptolites. 175 



Scandinavia, and its range must extend at least from the 

 lowest beds of the Arenig formation to the middle strata ot 

 the Bala. 



Family Lasiograptidae. 



29. Lasioqraptus retusus, sp. nov. 

 (PI. V. figs. 24 a-24 d.) 



Polypary about one inch in length, with a uniform diameter 

 of one twelfth of an inch. Virgula capillary, distally pro- 

 longed. Septum zigzag. Hydrothecaj thirty-six to the inch, 

 once and a half as long as broad, arranged alternately, each 

 in contact with those of the opposite series for two thirds of 

 its length ; ventral edge very short and devoid of ornamenta- 

 tion ; aperture broad, horizontal, opening within the ventral 

 margin of the polypary ; excavation triangular in form, occu- 

 pying one third of the transverse diameter of the polypary 

 and about two thirds of its ventral margin. , 



The polypary in this very distinct form possesses, in a 

 marked degree, the essential characteristics of the genus 

 Lasiograjytus, with the exception of the marginal meshes 

 (amentula), which are absent in the specimen figured. The 

 zigzag septal line formed by the adpressed bases of the two 

 opposed series of hydrothecge is beautifully exhibited, and its 

 distinctness in position from the virgula proper is placed 

 beyond question by the straggling position of the ridge 

 formed by the latter upon the exposed face of the polypary. 



The hydrothecse are very similar in form to those in Lasio- 

 graptus Harknessi, Nich. sp. ; but the excavation is deeper 

 and more conspicuous. Each theca is in contact with two of 

 its nearest neighbours of the series on the opposite margin of 

 the polypary, the median line of separation forming a very 

 peculiar zigzag longitudinal seam on the face of the fossil. 

 Each is subquadrangular in general form, and is inclined at 

 an angle of about 45° with respect to the main axis. A deep 

 excavation occupies at least two thirds of the ventral margin ; 

 the remaining third is perpendicular and shows a slight trace of 

 ornamentation at the lower sinus. The aperture is horizontal 

 or but slightly concave, and opens entirely within the suc- 

 ceeding excavation. 



The species is easily separated from Lasiograptus Harlc- 

 nessi, Nich., and L. margaritatus, Lapw., by the general form 

 of the polypary. Only two specimens have beeD collected ; 

 the gonosome or amentulate form is as yet unknown. 



Horizon and Locality. Upper Llandeilo shales of the 

 neighbourhood of Llandrindod Wells, Radnorshire. 



