88 On an Amioid Fish from Brazil. 



region arc larger and stoutor and trnicli inclined backward.s. 

 In the part of the caudal region up to and including the first 

 liffinial support of the caudal fin there are tiiirty vertebral 

 centra, but only fifteen neural and htenial spines, so that 

 throughout tliis length the contra are diiplicafed in the pecu- 

 liar manner so characteristic of the anterior part of the caudal 

 region in Amiu. Similar duplication of the first two or tliroo 

 vertebrfe within the tail is also observable. The relatively 

 small centra in the upturned end of the caudal series corre- 

 spond in number at least with their apposed hajmal spines. 

 Of the sixteen or seventeen haimal arches supj)orting the 

 caudal fin all except the uppermost are stouter than tlic other 

 htemal arches and have their spines expanded distally to bear 

 the fin-rays. 



The rays of all the fins are stout, closely articulated, and 

 finely divided distally. The rather small pelvic fins ( plv.) 

 are crushed together, but the anterior border of one is distinct 

 and shown to be fringed with slender fulcra. The pelvic fin- 

 supports resemble those of Arnia in shape. The dorsal fin 

 arises immediately opposite the insertion of the pelvic pair, 

 and comprises only about fifteen rays, of which the foremost 

 two or three are short and small. It is acuminate in front 

 and somewhat deeper than long, the complete extent of its 

 base-line not exceeding the interval between the pelvic and 

 anal fins. The anal fin (a.) is much smaller and shorter than 

 the dorsal, with ten rays. Its anterior border is well |)re- 

 served, but does not show any fulcra. The caudal fin (c.) is 

 very large, with relatively stout rays. It is disturbed at its 

 liinder margin, but does not appear to have been forked. 

 The scales are very thin and deeply oveilapping, ovoid in 

 shape, and marked with delicate concentric lines. 



The only Amioids with complete vertebral centra suffi- 

 ciently well known for comparison with the new youth- 

 American fossil now described are JlJegaluruSj Amiopsis, and 

 Anna. Amia is distinguished by the great extent of its 

 dorsal fin ; while ^?y<?'o/vs/s differs not in this character, but in 

 the deep ])itting of the sides of its vertebral centra*. Tiic 

 typical Me(jalurus^on the other hand, agrees in all particulars 

 which can be compared. Mr, i\lawson's specimen may tiiere- 

 fore be referred to the latter genus, of which it represents a 

 hitherto unknown species, to be ajjpropriately named Mega- 

 lurus Mawsoni. The dorsal fin-rays are fewer and the anal 

 fin is slightly more remote than in any of the typical species 



• See especially U. G. Kraiuberger, Djcla Jugoslav. Akad. vul. xvi. 

 (1895) p. 17, pL iii. fig. 2, pi. iv. 



