Palaeozoic Bivalved Entomostraca. 403 



more pyriform ; and there is a small furrow below instead of 

 above it, and directed towards a small pit iu the middle of the 

 anterior third of the valve. 



Fig. 12 shows a higher subovate carapace, with one ob- 

 lique sulcus, somewhat like that in fig. 9 a, but shorter and 

 deeper ; and there is a pinching-in of the ventral region, ob- 

 scurely connected with a rather large obliquely oval pit ante- 

 riorly. 



Figs. 11 and 12 might be grouped as var. unipunctata. 



Fig. 13 has a large, oblique, pyriform sulcus across the 

 posterior moiety, much like that in fig. 11, and the ventral 

 region has a median oblique depression leading up into a rather 

 large oval pit, immediately above which is another such pit, 

 so that an oblique, convex, fold-like elevation of the shell 

 divides the two pits from the posterior sulcus. This form may 

 be separated as var. hipunctata. 



All the known ThlipsurcE are evidently closely related 

 among themselves as far as the evidence of the carapaces can 

 show, the modifications of outline, contour, and surface- 

 markings being relatively slight from stage to stage. The 

 soft parts, however, of the animals being unknown, and pro- 

 bably important in their differences, we must give the more 

 credit to the changes in the form of the valves, as often 

 noticed in former papers on fossil Entomostraca. 



C Vine Coll. Fig. 10. xvig."^ t> ^ o^ qi i 

 -ri \ ^-^ -, -, ^,,/ ( Bed no. 26. Shales 



iour I i^ig. 11. xvig. 



specimens : \ Fig. 12. xvi^. 



( Fig. 13. XVI5. 



over Wenlock 

 Limestone. 



5. Thlipsura v-scinpta^ J. & H. 



Thlipsura vscrvpta, J. & H., Ami. & Mag. Nat. Hist. ser. 4, vol. iii. 

 p. 214, pi. XV. figs. 3 a-c. 



Proportions :—L. 16^. H. 10^. Th. 9. 



The angular sulcus on the hinder half of the valve may be 

 looked upon as an intensified form of the posterior depressions 

 in Till. anguLata and plicata^ and the anterior sulcus as corre- 

 sponding with, but much more definite than, the pits in the 

 varieties unipunctata and hiininctata of Till, plicata. Thl. 

 v-scripta was referred to by Mr. Vine in the Q. J. G. S. 

 vol. xxxviii. p. 48, as Thl. corpulenta, var. scripta. 



This species, in 1869, we found rare in the Wenlock Lime- 

 stone ; a few more have been met with by Messrs. G. R. 

 Vine and J. Smith. It is extremely abundant in the Silu- 

 rian Limestone of Scandinavia (Ann. & Mag. Nat. Hist. 



