138 XE. J. MAWS01T A>~I) DE. A. SMITH W00DWABD OX [^lay I907, 



latter period. The unique tooth of Acrodus nitidus is very small, 

 and belongs to a diminutive shark like that indicated by the equally- 

 small teeth of Acrodus ornatus from the Wealden of the Isle of 

 Wight. The vertebrate fossils, therefore, confirm Hartt's determina- 

 tion of the Bahia estuarine deposits as referable to the beginning 

 of the Cretaceous Period. It is certainly disappointing to find that 

 at that time the land in the South- American region was as destitute 

 of mammalian life as the continent in the Northern Hemisphere 

 drained by the river which deposited the VTealden formation of 

 Western Europe. 



EXPLANATION OF PLATES VI-VIII. 

 Plate VI. 



Figs, la & lb. Goniopkolis Hartii (Marsh) ; the greater portion of the 



mandibular symphysis, oral aspect (1 a), with anterior expansion (1 b) 



seen from below, one-quarter of the natural size. — Setiibal. [Brit. 



Mas., No. E 3423.] 

 Fig. 2. Ditto ; incomplete dorsal scute, outer aspect, showing the antero- 



external peg, one-quarter of tbe natural size. — Ponta de Tinuaba. Ilha 



Mare. [Brit. Mus., Ho. E 3224.] 

 3. Steneosaarus sp.; dorsal scute, outer aspect, showing the antero- 



external peg. three-quarters of the natural size. — Oxford Clay; 



Peterborough. [Collection of Alfred N. Leeds, Esq. ; F.G.S.] 

 Figs. 4 & 5. Belonostomtis (?) carinatas, sp. nor. ; scales, partly broken, 



probably of the caudal region, natural size. — Itaearanha. [Brit. Mus.. 



No. P 10062.] 



Plate VII. 



Fig. 1. Mawsoma gigas. gen. et sp. nov. ; remains of skull and mandible, 

 right lateral aspect (type-specimen). [Brit. Mus.. No. P 10355.] 



2. Ditto ; left frontal of the same specimen, outer aspect. 



3. Ditto: left quadrate of the same specimen, outer aspect. 



Figs. 4 a & 4 b. Ditto ; right parietal of another specimen, outer aspect (4 a),. 

 with (4 6) transverse section of edge of bone, showing overhanging 

 outer lamina, natural size. [Brit. Mus., No. P 10356.] 



ag. := angular ; art. = articular ; hr. = displaced branchial arches; go. = 

 coronoid ; or. = cranium ; hm. = top of hyomandibular ; ot. = otic region ; 

 pas. = parasphenoid ; pit. = front end of ectopterygoid ; pts. = pterygo- 

 suspensorial plate ; qu. = quadrate. 



Plate VIII. 



Figs. 1 a & lb. Mawsonia gig as, gen. et sp. nov. ; left articular of type-specimen, 



outer (a) and (b) condylar aspects. 

 Fig. 2. Ditto ; posterior end of the left mandibular ramus of the same specimen, 



outer aspect, showing the meckelian ossification (m.) projecting 



beyond the angular bone (ag.). 

 3. Ditto ; left coronoid of the same specimen, inner aspect, showing the 



granular teeth and facette (J.) for the overlap of the splenial. 

 Figs. 4 a & 4 6. Ditto ; portion of ectopterygoid of the same specimen (4 a) 



inner aspect, natural size, and (4tb) some teeth enlarged 15 times. 

 Fig. 5. Ditto ; gular plate of the same specimen, outer aspect. 



6. Ditto ; portion of right operculum, outer aspect, showing place of 



suspension (s.). [Brit. Mus.. No. P 10357.] 



