108 TRILOBITES OF GIRVAN. 



It has been thought that the head-shields which were attributed to L. hibemicus 

 by Portlock and others should be separated off from the pygidium and thorax 

 forming the original type of L. hibemicus (Portlock, op. cit., pi. iv, fig. 1 c), and 

 that quite a different type of pygidium should be associated with them. The 

 reasons for this view were first brought forward by Schmidt (op. cit., p. 29), and 

 more recently were referred to by the author {op. cit.). The character of the 

 ornamentation in the Irish forms seems to support this view. But this splitting 

 up of an old-established species may be considered of somewhat doubtful wisdom 

 till we have had our suspicions confirmed by a complete individual showing both 

 the head-shield and pygidium in connection. 



Head-shields of the type usually called L. hibemicus occur at Craighead, but no 

 pygidia are known. From Balclatchie, however, in the Edinburgh Museum there 

 is a pygidium resembling Portlock's type, and agreeing in style of ornamentation 

 with the head-shields which Schmidt would separate off, and which occur in the 

 same locality. No other species of Liclias (save one poorly-preserved specimen 

 of a peculiar head-shield (p. 110), specifically indeterminable, from the Balclatchie 

 conglomerate) is known from this locality, so the natural presumption is that this 

 pygidium belongs to the same species as the head-shields named L. hibemicus. It 

 does not entirely agree with Portlock's type, as it shows two complete rings on the 

 axis and a third ring incomplete in the middle ; but the pleurae are similar, only 

 the first two pairs having furrows, and their extremities are not preserved ; and 

 the post-axial piece has precisely the same general characters. It may indicate 

 a variety of the species. 



There is a hypostome from Balclatchie in Mrs. Gray's collection which may 

 probably be referred to L. hibernicus. Its description is as follows : — Body sub- 

 circular, a little broader than long, convex, with sides marked by a pair of strong 

 short horizontal lateral furrows at about one third the distance from posterior end. 

 From the inner end of these furrows two short narrow ridges run obliquely back- 

 wards and inwards. Axial furrows deep, strong. Border in front of body narrow, 

 prolonged laterally into upwardly directed pointed wings, behind which it becomes 

 strongly swollen and excavated opposite the lateral furrows of the body. Behind 

 these furrows the border rapidly widens, becomes flattened, and is produced laterally 

 into a second pair of pointed wings directed upwards. Behind the body the border 

 is produced into a pair of rounded flattened approximate lobes. Some faint con- 

 centric striae ornament the sides of the body and the border. 



Dimensions of hypostome. — 



Length . . . . .12*0 mm. 



of body . . . . 8-0 „ 



Width of „ . . . . 10-0 „ 



Collections. — Mrs. Gray ; Museum of Practical Geology ; Edinburgh Museum. 



