SHUMARDIA PUSILLA. 43 



" From the type species of the genus, the Shumardia granulosa of Billings, 1 

 8. pusilla is distinguished by its more quadrate tail, and by the absence, in the 

 adult, of the groove from the apex of the glabella over the frontal limb. 



" Shumardia scotica, Reed ~ (from the Bala beds of Whitehouse Bay), is 

 readily distinguished. Thanks to the kindness of Mrs. Gray the writer has had 

 the privilege of examining the type specimens. The proportions are noticeably 

 different, a line across the glabella at the back of the lateral lobes dividing it into 

 two equal parts, Avhereas in 8. pusilla a similar measurement gives 15 : 23 as the 

 proportion of front to back. The lateral lobes are more prominent and better 

 defined on their inner sides, while the furrows round the front of the glabella are 

 deeper. The prominent tubercle on the neck-segment (apparently a backwardly 

 directed spine), and the strong posterior furrow on the cheek also distinguish it. 

 The genal angles are not sufficiently disclosed to show their form." 



To the above observations by Mr. Raw I have only to add the following notes : 



The tubercles on the thorax and tail are most clearly seen on external moulds, 

 and are often indistinct or even invisible on internal casts. The ridges on the tail 

 are not always well shown, and this is especially the case with the fine inter- 

 mediate ridges which correspond with the raised edges of the pleuras in the thorax. 

 The long spine of the fourth segment is often buried in the matrix, and requires 

 careful development to disclose it. It may be remarked that even in the Shineton 

 specimens, which are usually well preserved, Callaway does not appear to have 

 observed it. It should, indeed, always be borne in mind, in dealing with specimens 

 of this genus, that the margins of the head and tail and the ends of the pleura? are 

 very commonly concealed. 



Specimens precisely similar to those from Shineton occur at several localities 

 near Arenig. The very fine example shown in Plate III, fig. 20, for the loan of 

 which I am indebted to Mr. Gr. J. Williams, was found by him at Amnodd Bwll in 

 that district. It is one of the largest that I have seen, measuring 4 mm. from 

 head to tail. 



Horizon and Localities. — Upper Tremadoc : Shineton (in the Shineton Shales) ; 

 Amnodd Bwll, and other localities near Arenig; Malvern. 



la. Shumardia pusilla, var. morvensis, var. no v. Plate IV, fig. 5. 



The specimens of Shu?nardia found at Penmorfa closely resemble those from 

 Shineton, and must, I think, be referred to the same species; but they present 

 certain small differences which, although minute, appear to be constant, and thus 

 constitute a distinct varietv. 



1 Paleozoic Fossils, vol. i (1865), p. 92, fig. 83, a, b. 



- Trilobites of the Girvan District, Palaeout. Soc, 1903, p. 42, pi. iv, fig. 12. 



