450 ME. A. WADE ON THE LLANDOVERY AND [Aug. I9II, 



"while its concave character also serves to distinguish it. The 

 carinated glabella, too, is a characteristic feature. 



From Trinudeus lloydii x it is distinguished by the subtriangular 

 tail, -which approximates in shape to that of Tr. concentricus. 

 The concavity of the fringe is not so marked as in Tr. lloydii, 

 while the indentations in the furrow surrounding the glabella in 

 that species are either obscure or absent. The arrangement of the 

 pits in the fringe is also different : in Tr. lloydii the pits are more 

 closely set on the inner margin, while in Tr. intermedins they are 

 more closely set on the outer margin of the fringe. The species is 

 distinctly intermediate in character between Tr. concentricus and 

 Tr. lloydii. 



Hall's figures of Tr. concentricus seem to bo nearer to Tr. lloydii 

 than to Tr. concentricus. They correspond with Tr. intermedins more 

 closely than with either, and differ chiefly in having shorter spines. 

 The species figured in his pi. lxv differ also in the disposition of 

 the pits, the larger pits being on the outside of the fringe. Those 

 figured in his pi. lxvii correspond more closely in this respect. 

 The grooves in the furrow, round the glabella, characteristic of 

 Tr. lloydii are obscurely indicated in Hall's figures. The tail, how- 

 ever, is subtriangular, and the glabella encroaches on the fringe, 

 both features characteristic of Tr. intermedins, and not of Tr. lloydii. 

 On the whole, therefore, Hall's species correspond more closely to 

 the species now described, although they are slightly nearer to 

 Tr. lloydii than is the new species, thus affording a further link in 

 the chain of evolution. 



Horizon and locality. — Trilobite-Dingle Shales, Welshpool. 



Dionide sp. ? (PI. XXXYT, fig. 3.) 



Length = 11*8 millimetres ; width =12*5 mm. Shape nearly cir- 

 cular. Head equal in length to rest of body. Glabella large, almost 

 circular, slightly contracted behind ; somewhat swollen, bearing two 

 pairs of furrows, more or less obscure, which die out towards the 

 axis of the glabella. Cheeks about equal in width to the glabella, 

 and bearing a groove which runs directly forward from the posterior 

 margin at about a quarter of its length from the glabella, and 

 meeting the glabella in its widest part. Anterior part of head- 

 shield not preserved. 



The body consists of six flat segments, the axis being slightly 

 raised and rather more than a fifth of the width of the thorax. 

 Pleurae straight and horizontal, grooved by a strong diagonal furrow 

 which divides them unequally. 



Pygidium rounded or subtriangular, with entire margin. Axis 

 conical, and bearing eight or nine rings which become small and 

 obscure anteriorly. There are six lateral lobes, each somewhat 

 fusiform in shape and grooved diagonally in a manner similar to 



1 J. W. Salter, * Brit. Organic Rem.' Mem. Geol. Surv. dec. vii (1853) pi. vii. 



