THE ANCIENT ROCKS OF ST. DAVID'S. 185 



one half the whole length ; posterior margin arched backwards. 

 Glabella very wide anteriorly, but narrowing rather abruptly 

 towards the neck, axial furrows moderately strong and extending 

 obliquely to the outer margin. Eyes large and placed at a distance 

 equal to their length from the outer margin. Free cheek triangular 

 in shape, and not produced posteriorly ; neck-furrow deep. Thorax 

 composed of ten rings ; axis well raised, tapering gradually towards 

 the tail, and about equally wide with the lateral lobes ; pleurae 

 faceted and deeply grooved to the tips, which are rather abruptly 

 pointed. The tail acutely triangular ; axis strong and composed of 

 several rings ; lateral lobes raised, with a strong outer margin, which 

 is widest opposite the axis. 



The only other species known is Lllamopsis Thomsoni,; and from 

 this our species differs in the following points : the glabella is 

 wider, the eye much larger, and the occipital furrow reaches the 

 outer margin much lower down ; the pleurae are more blunt, and the 

 tail shorter and more triangular in shape. 



Looality and Formation. Llanvirn Quarry : Upper Arenig. 



JEglina Boia, Hicks, Cambridge Catalogue, 1872. PI. X. figs. 9, 9 a. 



This little species was discovered by me in the year 1865, in the 

 Middle Arenig rocks at Whitesand Bay. The only specimen found 

 is in the Cambridge Museum. It is a small smooth species, with no 

 grooves or markings visible on the head and tail, and it seems dis- 

 tinct from any species hitherto published. 



Locality and Formation. Whitesand Bay : Middle Arenig, 



^Egltna obtusicatjdata, n. sp. PL X. fig. 3. 



The specimens of this species hitherto found are imperfect, but 

 they are sufficient to show that it is a new species. 



Description. — About 2 inches long. The head is imperfect, but it 

 appears to occupy about half of the whole length. Thorax of six 

 rings ; axis very wide anteriorly, and tapering backwards rather 

 suddenly, moderately raised. Anterior pleurae very short, hinder 

 ones increasing gradually, so that the last is about twice the length 

 of the anterior one ; they are grooved deeply and are obliquely 

 truncate at their extremities. Tail about a fourth of the whole 

 length, wider than long ; posterior border bent slightly forward and 

 incurved ; axis conical and extending to the posterior incurved 

 margin. 



The wide short tail, with bent margin, distinguishes this from any 

 other British species. 



Locality and Formation. Llanvirn Quarry : Upper Arenig. 



Bakrandea Homfkavi, n. sp. PL IX. fig. 8. 



Hitherto the genus Barrandea in this country has only been 

 found in Upper Llandeilo rocks ; but in Bohemia M. Barrande has 

 found a species in his Etage D. 1, which is probably equal in age to 



