12 



BRITISH FOSSILS. 



are no lateral jugular plates, but the principal jugular plates are 

 separated, anteriorly, by an azygos rhomboidal plate. 



The family of the Saurodipterini, characterized by its two 

 dorsals; less acutely lobate paired fins ; jugular plates and no bran- 

 chiostegal rays ; smooth scales and cranial bones (among which last 

 are three distinct occipital plates, while the other cranial bones have 

 more or less coalesced), is thus very distinct from, though allied to, 

 that of the Glyptodipterini. It comprises not only the genera 

 Osteolepis, Diijloptems, and Triploj)terus {?), but also, as I believe, 

 a genus w^hich has a later range in time than these, viz., the 

 Megalichthys of the Coal, although the want of acquaintance with 

 'the fins of this genus renders my conclusions as to its afiinities 

 less secure than I could wish.* Agassiz does indeed afiirm that 

 Megalichthys has lobate fins, in a passage cited above (p. 7); but as he 

 merely mentions the fact incidentally, I do not like to lay too much 

 stress upon it. Nevertheless, the skull and scales of Megalichthys 

 accord so closely, both histologically and morphologically, with those 

 of the better known Saurodipterines, that I entertain little doubt 

 as to its real place in the latter family. 



Megalichthys has two principal, many lateral, jugular plates ; 

 and a single rhomboidal, azygos plate is placed between the 

 anterior ends of the two principal jugulars. Between the upper 

 margins of the opercula and in the upper occipital region, lie three 

 bony plates, whose signification Professor Agassiz considers to be 



somewhat enigmatical/' but which really correspond exactly 

 with the three bones which occupy the same position in the 

 Glyptodipterini and Saurodipterini. What Agassiz terms the 

 frontals are certainly the long parietals, whereas those which 

 he calls " ethmoids are the frontals. His " moignon intermaxil- 

 " laire" is a crescentic shield, which terminates the head ante- 

 riorly, and presents distinct indications of a division into a 

 number of pieces ; the contour of the proper premaxillary portions, 

 separated by a median suture, which form the lower and anterior 

 boundary of the shield, being very well defined. The other parts 

 entering into this shield represent, I believe, the prefrontals and the 



* Sir Philip Egerton long since arrived at and published this conclusion in his 

 arrangement of the Fossil Fishes in Morris's Catalogue. More recently Prof. Pander 

 expresses the same conviction in the following terms : " Sehr gerne mochten wir aber ein 

 " anderes Genus noch zu den Saurodipteridse bringen, das durch den Bau seiner Kopf- 

 " knochen ; durch die Gestalt seiner Schuppen, seiner Zahne und hauptsachlich durch die 

 " mikrospische Structur seiner harten Theile sich eng an Osteolepis anschliesst und aus 

 " der Kohlenformation herstammt. Es ist der Genus Megalichthys, von dem wir leider 

 ' die Beschaffenheit und Lage seiner Flossen gar nicht kennen."^ — Pander, 1. c, p. 5. 



