264 Dli. W. G. KIUEWOOD OX TIU'. 



The bones are numbered and are referred to in detail in the text- 

 A copy of the uppermost figure of the plate was republished in 

 1814 without the numbers (Agassiz, Monog. Poiss. Foss. Vieux 

 Gres Eouge, 1844-45, pi. F : see also pp. 107-109 of the text). 

 The relations of the sculptured to the non-sculptured parts of 

 the bead are well show^n in the figures given by Yalenciennes 

 (Hist. Nat. Poiss. xix. 1846, pis. 579-582). 



Two skulls of Arapaima were available for study — a small 

 incomplete skull measuring 7 inches in length, and a full- 

 sized skull, about 16 inches long, forming part of an articu- 

 lated skeleton exhibited in the British Museum. The details of 

 the cranium, hyopalatine arch, and mandible were made out from 

 the small specimen, and figs. 12, 13, 14, and 16 were drawn from 

 this ; fig. 15, showing the superficial bones, was drawn from the 

 larger specimen. 



Cranium (PI. 32. figs. 12, 13, and 14). — The parietals are large, 

 and meet one another in the median line along their whole 

 length. The squamosals appear rather small as compared with 

 the parietals. The nasals are of considerable size and are 

 incorporated into the cranium ; they meet one another in a median 

 suture, and are suturally united with the anterior edges of the 

 frontals. The nasal, frontal, parietal, and squamosal bones are 

 sculptured on their upper surface, but each has a shallow 

 depression devoid of sculpturing, at the bottom of which is a 

 perforation where the tubes of the sensory canal-system come to 

 the surface. A median depression of a similar nature occurs 

 in the postero-mesial parts of the parietal bones, just in front of 

 the supraoccipital. The posterior, deep-lying part of the parietal 

 is relatively much smaller than in Osteoglossuvi, and forms but a 

 small semicircular lamina overlying the base of the epiotic promi- 

 nence. Neither the prefrontal nor the postfrontal comes to the 

 surface of the head, and neither is sculptured. 



There is a backwardly directed supraoccipital crest of small 

 size. The vagus foramen in the middle of the side of the 

 exoccipital is large, and in the part of the exoccipital bone which 

 forms the side of the foramen magnum there are three foramina, 

 as in Osteoglossum. The opisthotic is of moderate size ; it is 

 united with the epiotic, exoccipital, and squamosal, and with a 

 backward prolongation of the pro-otic A lateral depression 

 occurs in the upper part of the pro-otic bone ; the subtemporal 

 fossa is ill-defined and shallow. The j^osterior temporal fossa is 



