MACKOPOMA. 



27 



The Genus MACEOPOMJ, Agassiz. 



/. Macropoma Mantellii, Agassiz (Plates YII. and YIII.) 



Attention was first directed to this remarkable genus of Coela- 

 canth fishes, in 1822, by the late Dr. Mantell;, who, at page 239 of 

 his work " The Fossils of the South Downs," gives the following 

 account of the specimens which had fallen under his observa- 

 tion : — 



Amia ? Leioesiensis. Tab. xxxvii., xxxviii. 



"The length of this ichthyolite generally exceeds 18 inches, the 

 head being equal to one-third of the whole ; the width is about 4*5 

 inches. The body is of an elongated form, slightly compressed, scaly 

 and reticulated. 



The scales are of a rhomboidal shape, and beset with numerous small 

 adpressed spines, producing a scabrous reticulated appearance, not unlike 

 the surface of some kinds of Balistes. The head is angulated ; tlie 

 orbit large ; the opercula smooth and rounded ; the jaw dentated and 

 nearly straight. The teeth in the upper maxilla are conical, pointed, 

 and rather flat ; there are about 40 on each side, of which the eight or 

 nine anterior ones are the lai'gest. Those of the lower jaw are exceed- 

 ingly small and very numerous. The dorsal fins are two in number ; 

 the anterior one {a, Tab. xxxvii.) is placed in a sulcus or groove in 

 the back, and appears to have been capable of erection or depression ; 

 it consists of eight strong rays, the two first being garnished with 

 spines. The posterior dorsal fin {b, Tab. xxxvii.) is remote from the 

 other, and composed of numerous delicate rays. The pectoral fins are 

 placed on the thorax, near the lower margin of the opercula. The 

 ventral fins (c. Tab. xxxvii.) are attached to the abdomen opposite to 

 the anterior dorsal fin. The anal fin is unknown. The tail appears to 

 have been rounded, but no perfect specimen of this part has been ob- 

 tained. The tongue is occasionally preserved {vide Tab. xxix., fig. 6 ; 

 Tab. xxxiv., fig. 7.) It is of a triangular form, and its surface is covered 

 with numerous papilljB, The air bladder is of an elongated oval shape, 

 and lies in the abdomen immediately beneath the spine." * 



Dr. Mantell compares the fish with Mugil, Balistes and the 

 Amia ignota of De Blainville. 



In the third chapter of the second part of the second volume 

 of the " Keoherches," Agassiz established the genus Macropoma 

 for the fishes discovered by Mantell ; and he describes the 

 characters of the new genus and discusses its relations in the 

 following terms : — 



" It is incontestable that this genus has striking afiinities with 

 the genus Ccelacanthus. The body is similarly thick, and the fins 

 have a like arrangement. There are, as in Ccelacanthus, two dorsal 

 fins, one of which lies opposite the interval between the pectorals and 

 the ventrals, and the other opposite the space between the ventrals and 

 the anal. The second dorsal is supported by a very strong bone, which 

 is also found in many other genera of the family. The caudal is largely 



* " It may seem scarcely credible that a part of such delicate structure should be 

 preserved in a mineralized state, yet the fact is unquestionable. I have three speci- 

 mens in my collection in which it is clearly shown." 



