PTERYGOTUS BILOBUS. 69 
long. broad. 
Head (1—7) 15 lines by 2 inches. 
Body-segment (8) Ate Dia. 
eS (9) On ee. 2 lines. 
= (10) i ee ae Ar 
= Bs (11) OWE ieee cores 6. 
| 7 (12)? 5 ee eee en ome 
f (13) DT ay Lats, DRS 
3 (14) 4 ior kee Di AS 
- (15) OR ele Olas eae 
| i (16) Oi | ieee 7A ia 
= _ (17) 6" s tomes Nao 
E k (Gs). 6. i ge eee 
= " (isin! gock, dilah) Arata, 
Telson G20)! FAlStasss pla S 1 line 
The surface of the head is not ornamented in any way, but the bases of the jaw-feet, 
the thoracic plate (see Woodcut, fig. 13), and the anterior third of the body-segments, 
are closely covered with minute plice. 
The portion of magnified scale-markings drawn by Mr. Hollick in Pl. XII, fig. 
1 ¢, are from the body-segment (10) ; the squame are so close together that they actually 
present the appearance represented, but there is no real overlapping of scales, only a 
mimetic resemblance to it. Along the anterior border the scale-markings are very fine, 
closely packed, and but little arched ; lower down they become more acute and consider- 
ably larger ; whilst on the lateral borders they are extremely minute and packed very close 
together. ‘The edges of all the segments are very minutely serrated, as in the larger 
Devonian species. ‘The thoracic plate, which is very well preserved, is about 2 inches 
in breadth by about 10 lines in length. 
f f 
( 
Fig. 13. Thoracic plate or operculum of Pé. dilobus, var. 6. 
a, a. Line of attachment to posterior border of head-shield. #f. Free border. c. Central appendage. 
' The representation of the operculum in Pi. XII, fiz. 1 e, is not quite correct. This Woodcut conveys 
a better idea of its form. 
10 
