[MATTHEW] STUDIES ON CAMBRIAN FAUNAS 179 



Size. — Length (including the occipital spine) and breadth of the 

 centre piece of head -shield, each about -4J mm. 



Horizon. — Found with the preceding species. 



This species has a general resemblance to Agrauloa Whiffieldianus of 

 the Eteminicus sub-fauna of the St. John basin, but is much smaller and 

 has a proportionately larger glabella. Both these species are from lime- 

 stone conglomerate bands, but at ditïerent horizons in the St. John 

 Group. 



The preceding small species A. (?) nanus and A. (?) pusillus are of 

 those forms which approach Ptychoparia, about whose proper generic 

 place there is doubt. This one has the deep dorsal furrow of Soleno- 

 pleura, but the straight dorsal suture and the arched anterior outline of 

 the head are Aarrauloid. 



LIOSTEACUS, Angelin. 



LiosTRACus VALiDus, n. sp. (PI. II., tigs. 7 a and h.) 



Only the middle piece of the head-shield is known ; this, exclusive of 

 the occipital spine, is sub-trapezoidal in outline. The front margin is 

 upturned, and the marginal furrow shallow and broad. The width of 

 the front area and fold is equal to that of the cheek behind the eyelobe, 

 or of the occipital ring and spine together. The glabella is conical, 

 rounded in front and without furrows. The fixed cheek is two-thirds of 

 the width of the glabella, has a faint ocular fillet and the eyelobes are 

 opposite the anterior third of the glabella ; there is no occipital furrow 

 on the axis of the shield, but the glabella passes by a gentle curve into 

 the occipital ring. The posterior furrow and fold are well marked, and 

 the dorsal furrow well defined. 



Sculpture. — The surface is smooth. 



Size. — Length of the head-shield, including the occipital spine, 

 11 mm. ; width of the middle piece at the front, 17 mm. ; at the eyes, 

 10 mm. ; at the posterior angles, 13 mm. 



Horizon. — From a conglomerate-limestone band in the gray shales. 

 Infrequent. 



In the form of the middle piece of the head-shield this species is 

 closely related to L. Ouangondianus of the St. John basin, and to L. 

 aculeatus of the Paradoxides beds of Sweden. It differs in having a 

 larger glabella and stouter occipital spine. As only the middle piece of 

 the head is known, no comparison can be made with other parts of the 

 animal. 



