244 l)r, K. 11. Traquair om the Structure 



where this relation has been left undisturbed *. These inter- 

 clavicular ])lates are certainly the structures whicli have been 

 ligured anil doHcribed by I'owrie as " principal jugulars" — a 

 mistake into which he never could have t'^lU'ii had he observed 

 their relation to the clavicles, or had he taken into considera- 

 tion the stnicture of the shoulder-girdle in the recent Polypterus 

 or in the extinct Palajoniseidie. And in the presence and con- 

 figuration of this, as of all the other elements of the shoulder- 

 girdle, the closest resemblance is seen between Chcirolepis and 

 the genera of fossil fisiies allied to Pahvoniscus, for corroboration 

 of which the reader need only refer to my description of the 

 same parts in Cydoptychiics carhonariiu>i\, and in Fygoptcrus 

 [Nematoptychius) Greenockii and Ainhlypterus pu7ictatiis\. 



Passing now to the bones of the Jace, we find the most 

 singular conformity to the general type of structure in Paloio- 

 niscus and its allies — a fact which, as already mentioned, did 

 not altogether escape the notice of Pander. In the first place, 

 the gape is very wude, the direction of the axis of the suspen- 

 sorium and of the opercular apparatus passing obliquely down- 

 wards and backw^ards, so as to carry the articulation of the 

 lower jaw far enough behind. The superior maxillary bone 

 (PI. XVII. figs. 1 & 7, mx) has been very eoiTcetly figured by 

 Pander, and is formed on the same type as in all the Palaio- 

 niscidse. It consists of a plate of bone, broad behind the eye, 

 and there covering a large part of the cheek ; but immediately 

 behind the orbital ring the superior margin becomes suddenly 

 cut out, so that the anterior extremity passes forwards below 

 the orbit, tapering to a ])oint towards the prcmaxillary region. 

 The inferior or dental margin is not quite straight, but shows 

 a slight sigmoid curve ; tlie posterior inferior angle is rounded, 

 while the short posterior margin, sloping obli(|uely upwards 

 and forwards, joins the straiglit part of the superior margin 

 at a very obtuse angle. Closely articulated to the maxilla 

 is a rather narrow plate (fig. 7, x)^ consisting of two parts 

 diverging at an obtuse angle. The upper and anterior of 

 these lies along the superior margin of the maxilla behind 

 the orbit, the lower and posterior one passing down for some 

 distance along the oblique posterior margin of the same bone, 

 between it and the suboperculum, the centre of ossification 



* Though in the specimen represented in Plate XVII. fig. 2 the inter- 

 clavicles liave been forced apart, their juxtaposition is beautifully shown 

 in No. 41725 of the British-Museum collection, and many others which 

 I have seen. They are also in contact with each other in Mr. Powrie's 

 figure ; but there both are also diisjoincd from their respective clavicles. 



t Geol. Magazine, 2nd series, vol. i. June 1874. 



t Trans. Royal Soc. Edinburgh, 1867, xxiv. pp. 707, 708. In this 

 paper I called th*' interclavicular /'/vro/rtcojV/. 



