PARABOLINELLA RUGOSA. 67 



3. Parabolinella rugosa, Brogger, var. Plate VIT, fig. 3. 



1882. Parabolinella rugosa, Brogger, Die Silur. Etagen 2 und 3, p. 104, pi. iii, fig. :>. 

 1896. Parabolinella, sp. nov., Crosfield and Skeat, Quart. Journ. Geol. Soc, vol. Iii, p. 537, pi. xxvi, 

 figs. 11, 12. 



Glabella almost square, narrowing slightly towards the front. Four pairs of 

 glabellar furrows; the first pair nearly parallel to the neck-furrow, somewhat sinuous; 

 the second pair rather more oblique and also rather sinuous; the third pair strongly 

 curved, the convexity directed forwards, giving off a posterior branch towards the 

 axial groove ; posterior furrows nearly straight and nearly at right angles to the 

 axis, bifurcating inwards, a narrow ridge being enclosed between the branches. 

 Neck-segment divided by a groove passing from one posterior lateral angle to the 

 middle of the neck-furrow and thence to the other posterior lateral angle, a small 

 tubercle on the middle portion thus separated off. Eye placed very near to the 

 glabella, large, extending from the second nearly to the last glabellar furrow ; 

 ocular rido;e verv short, reaching the axial groove close to the first Glabellar furrow. 

 Facial suture incompletely shown, but the posterior branch runs nearly parallel to 

 the posterior margin to a distance from the glabella about equal to three-quarters 

 of the width of the latter ; it then turns back to cut the margin. 



This specimen was originally described and figured by Misses Crosfield and 

 Skeat, who compared it with Brogger's P. rugosa and came to the conclusion that 

 it presented sufficient differences to be considered a new species or variety. 

 Owing, however, to the imperfection of the specimen they did not give it a name. 

 Whether it is identical or not with /'. rugosa, it is certainly very closely allied to 

 that species, and such differences as there are may be due to differences in the 

 mode of preservation. Until more perfect material has been obtained, therefore, I 

 prefer to consider it a variety rather than a distinct species. 



The glabella is wider in proportion to its length than in P. rugosa, but this is 

 clearly the result of compression. The only difference of importance is the peculiar 

 forking of the last pair of glabellar furrows. In such a specimen it is difficult to 

 distinguish between adventitious wrinkles and original furrows, but the fact that 

 both the right and the left furrows show the forking certainly suggests that it is 

 original. Brogger makes no mention of any such forking ; but his specimen is 

 from the Ceratopyge Limestone and may possibly show the actual test, while the 

 specimen of Misses Crosfield and Skeat is an internal cast. Moreover, a very 

 similar cranidium has been obtained from the same beds by the Geological Survey, 

 and in this there is no forking of the fourth pair of furrows. The precise form of 

 the glabellar furrows in such specimens as these evidently depends in part upon 

 the crushing to which they have been subjected. Misses Crosfield and Skeat 

 remark on the absence of a median tubercle on the neck-segment in their specimen ; 



