﻿ix, d. i Day: Ophlocephalus striata* 27 



on the inside, which passes along the inside of the hyomandi- 

 bulars (10). The outside of the right bone is shown in Plate 

 VII and the inside in Plate VIII. The left is also included in 

 Plate I. 



The symplectics (9) consist of a somewhat curved central 

 triangular portion with the base upward, and anteriorly and 

 posteriorly from this extends a wing-like process. They articu- 

 late with the metapterygoids (8) anteriorly, while the pointed 

 ventral portion becomes ankylosed with the inside of the quad- 

 rates (7). They are little more than laminate in the central 

 triangular portion only. The outside of the bone on the right 

 side is shown in Plate VII, and the inside of the bone on the 

 left side of the head is shown in Plate VIII. The left is also 

 included in Plate I. 



The hyomandibulars (10) consist of a somewhat columnar 

 head or dorsal portion, from which there projects a ventral 

 lamellar portion, reenforced in the middle region by a thickened 

 triangular area similar to that of the symplectics (9) with 

 which this portion of the hyomandibular articulates. From this 

 lateral part of the bone there projects, at right angles, into 

 the region of the accessory branchial chamber, a lamellar por- 

 tion, internally, which assists in supporting the membranes 

 there. The anterior portion of the head of the hyomandibulars 

 fits into a groove on the ventral surface of the sphenotics (39), 

 the posterior portion fits into a similar but shallower fossa 

 on the ventral surface of the pterotics (38), while the posterior 

 end of the head fits into the socket on the inner, anterior, upper 

 portion of the opercle (14). Ventrally they articulate with the 

 symplectics (9) and the metapterygoids (8), with the interhyals 

 (21) internally, and with the preoperculars (11) posteriorly. 

 They are perforated with canals continuous with those of the 

 preoperculars (11). The outside of the bone of the right 

 side is shown in Plate VII, and the inside of the bone on the 

 left side is shown in Plate VIII, while the left is seen in Plate I. 



The outline of the preopercles (11) is clearly shown in the 

 plates. Plate VIII shows the inside of the bone on the left 

 side, and Plate VII the outside of the bone on the right side. 

 They articulate with the hyomandibulars (10), the symplectics 

 (9), and the quadrates (7) anteriorly, with the operculars (14) 

 posteriorly, and the interoperculars (40) on the inside pos- 

 teriorly. On the inside they articulate with the interhyals 

 (21), which lie vertically on the preopercles (11). They are 

 perforated throughout the whole length by sensory canals. 



