•2o2 ME. W. K. PAEKEE ON THE STEUCTUEE AND DEVELOPMENT 



This obliquely placed plate runs almost directly forwards, and articulates by its 

 antero-superior bony centre to the outer angle of the crescentic dentary fore edge of the 

 corner — a constant relation of these bones in Carinate Birds ; it is seen also in Anguis 

 and Ilatteria. 



But the thin lamina of cartilage that formed the " model " for these three bones — 

 the quadrate (its front part), the pterygoid — and the mesopterygoid, is totally inde- 

 pendent of the palatine bone ; and the wliole arcade is very loosely connected by liga- 

 ment to that bone. 



The palatine (or rather " ethmo-palatine ") is a thick rod of ossified cartilage, lying 

 above the pterygo-quadrate plate, and reaching far in front of it. Behind, it ends above 

 the fore margin of the quadrate ossification, and in front reaches nearly to the angle of 

 the preemaxillary. 



In front it carries the arrested maxillary — the filament-bearer — which is wedged 

 between it and the prsemaxillary ; whilst the foremost of the two prseorbital ossicles, 

 that which becomes the " septomaxillary " of the air-breathers, rides upon its fore end 

 and also upon the fore end of the little maxillary. 



The most projecting part of the massive lateral ethmoid is a little in front of the 

 middle of this ethmo-palatine bar ; but the ethmo-palatine process is represented by 

 ligament, and the bone is everywhere loosely attached to the surrounding bones. 



Everywhere, above the Skate and its congeners, the exoskeletal bone that is related 

 to the " ethmo-palatine," as its proper splint, is the maxillary. This may be equally 

 well seen in Teleostean Fishes, Urodeles, Anura, and Carinate Birds. 



In bringing out this ethmo-palatine element of the face into bold relief, I have 

 done no violence to Nature, but only to my own confused and confusing prejudices. 



No " labial " element or " extravisceral " cartilage has ever been allowed to come into 

 my way in considering the true endoskeletal elements. I have used no cutting and con- 

 triving in trying to arrange morphological segments ; the parts are allowed to tell their 

 own story ; and listening to catch from them the least hint of their real meaning (I hold 

 my opinions almost loosely even), I am ready to cease from the folly of my own wisdom 

 at any moment, and adopt the truth, whenever and wherever I can unearth it^. 



DESCRIPTION OF THE PLATES. 



PLATE XXXIV. 



Fig. 1. First stage. Side view of an embryo of Dog-fish {Scyllium canicula), 8 lines 

 long, seen as a transparency, X 16 diam. 



' Whilst correcting the present paper (August 25th, 1877) I find in the Tadpole of Rana clamata four small 

 internal hranchial arches ; its pouched arches are " extrabranchials," and answer to the branchial " basket ' 

 of the Lamprey. 



