152 



fragmentary nature of the remains. Not a single instance of 

 an entire specimen has occurred, and only one in which one of 

 the free cheeks was attached to other portions of the cephalic 

 shield. The parts of the body usually recognisable are 

 the glabf^lla, the pygidium, occasionally an hypostome, and 

 several free cheeks, with eyes attached. No trace of a com- 

 plete, or even partially complete, thorax has been observed, 

 and the dismembered thoracic segments are not suflSciently 

 well preserved to admit of description. Under these circum- 

 stances, it may be imagined with what difficulty the piecing 

 together of these fragments has been attended. 



The genus Asaiolius is certainly represented by two tails, 

 probably indicative of distinct species. No other portions 

 referable to this genus have been noticed. We meet with 

 portions of a fine head, chiefly the glabella, which I cannot do 

 otherwise than refer to Conocephalites, and numerous examples 

 of a free cheek, with eye attached, and long genal spines, 

 which, perhaps, belong to the same genus. A fine pygidium 

 occurs in about equal abrmdance with the glabella just referred 

 to, possessing all the characters of the peculiar genus Dikelo- 

 cephalus. Now, by their size and association, these two i^ortions, 

 the glabella and tail, should belong to one individual, but we 

 cannot definitely unite them in the face of the different 

 characters a.ppertaiuing to the respective genera to which 

 they belong. It is strange that out of the large number of 

 specimens examined, no proper tail of a Conoceplialites, or head 

 of a Dikelocephalus, has been observed to complete the two 

 forms. Lastly there are a series of small head shields, all 

 more or less of the same type, but whose generic affinity, 

 owing to their fragmentary condition, must be left an open 

 question for the present. They clearly belong to the 

 Conocephaloid type, and appear to have affinities with certain 

 American genera of Trilobites. 



Description of the Species. 

 Genus CONOCEPHALITES (Zenker, 1833). Barrande. 1852. 



Obs. This genus includes Trilobites possessing a semicircular 

 head shield, with a very distinct neck, segment, and furrows. 

 The glabella is conical, attenuates forwards, and is divided by 

 three to four short furrows. The axr i grooves are deep and 

 broad ; the eyes present or absent, and placed either at the 

 anterior part of the head, beside the angles of the glabella, 

 or near the centre of the side lobes of the head. The course 

 of the facial suture is simple ; it commences at the anterior 

 margin of the head shield far out, turns inwards with a curve 

 towards the eye, and then curves towards the post angle and 

 cuts the margin. The pygidium is semicircular, with a 2-8 

 jointed axis, and slight furrows at the sides. 



The best descriptions of Conocephalites are those by 



