72 G. F. MATTHEW: ILLUSTRATIONS OF 



Cephalir shield broadly-tvansversely elliptical, high and contracted behind, sloping 

 IVom the glabella in all directions. Marginal fold and furrow strongly marked. Dorsal 

 furrow deep. G-labella suborbicular, rounded in front and behind, bearing a small tubercle 

 on the axial line, one third from the front ; the width of the glabella is more than a third 

 of that of the shield, and its length nearly half. 



The thorax is unknown. 



The pygidium is semi-elliptical, with rounded anterior corners ; the width is nearly a 

 quarter greater than the length. Both dorsal and marginal furrows are deeply impressed. 

 The axial lobe is conical and is greatly elevated above the rest of the shield ; it is slightly 

 constricted near the anterior end, and about one third from the front bears a small tubercle. 

 The lateral lobes of the pygidium are rounded in at the anterior end by the rapid curve of 

 the marginal furrow ; and at the posterior end are gradually narrowed, and are separated 

 at that end by a furrow which connects the dorsal and marginal furrows. The marginal 

 fold is rather wide at the extremity of the pygidium, and is rounded at the anterior corners. 



The head-shield of A. hrvif^alus, var. similis, of the Scandinavian beds, resembles this 

 species, but is nan-ower ; both this and the other forms of A. hevigatus, known to me, are 

 more elongated species than A. umbo ; and from the typical form of A. Jccvigaliis our species 

 is easily separated by the strong dorsal furrow on the head shield, 



Length, 6 mm. ? Width, 3 mm. 



Horizon and Locality. In the fine dark shales of Div. l.f/, at Porter's Brook. First 

 found in the shale from Porter's Farm collected by Professor L. "W. Bailey. 



Agnostus obtusilobus, n.sp. (Plate VII. Fig. 9.) 



Body elliptical oblong. 



Cephalic shield semi-elliptical, about one quarter wider than long. Dorsal furrow 

 faintly impressed. Marginal fold and furrow strongly marked. Glabella elliptical-elon- 

 o-ate, wider behind, rounded in front, in its widest part nearly a third of the width of the 

 shield ; narrowed at the base by two small triangular lobes ; a semi-elliptical lobe at the 

 anterior end more than one third of the length of the glabella. Occipital ring and 

 posterior marginal fold narrow. Cheeks continuous in front of the glabella. 



Thorax of two segments. The anterior segment has five lobes, of which the 

 outer pair are globose, and the inner pair subtriangular and widest in front ; the 

 centre lobe is semi-circular, broad behind, and bears an elongate, transverse tubercle 

 in the middle. The posterior segment has three lobes, of which each of the two lateral 

 ones is globose, and bears minute tubercles ; the central lobe is subrectangular elongate, 

 and the middle half is traversed by an arched furrow which begins and terminates on the 

 posterior margin of the segment. 



The pygidium is semi-elliptical, about one sixth wider than long, and has the 

 anterior margin arched forward. The marginal fold and furrow are about as distinct as 

 those of the head shield. The axial lobe is oblanceolate, constricted in the middle, clavate, 

 and pointed behind, about one third longer than wide ; it is traversed by three fun-ows, 

 of which the one near the anterior end arches forward, another near the middle arches 

 backward, and the third at the broadest part of the axial lobe is directly transverse. The 

 first segment of the axial lo])e is narrow and elevated transversely, the second segment is 



