part 2] GEOLOGICAL HISTOEY OF THE GENUS STEATIOTES. 127' 



3. Steatiotes actiticostatus, sp. nov. (PL V, figs. 5-6, 29-30 

 & PL VI, fig. 25.) 



I8fi9 I ? Folliculites parisiensis Brongniart 1 ,-r, . , „-. 

 '\?F. tlialictroides var. Brongniart | '" 



1862. ? Carpolithes websteri Brongniart (Heer & Pengelly 22). 

 1887. ? F. websteri Brongniart (Starkie Gardner 29). 



1889. < „' , , • -r, ■ , HBristow-Strahan-Reid 31). 



I? C. websteri Brongniart J v ' 



Seed oblong or narrowly oval, very slightly hooked at the base,, 

 flattened ; keel generally broad, especially in the larger and better- 

 developed specimens, continued as far as, but not round, the base ; 

 collar small, irregular, flattened below ; testa thick, woody, orna- 

 mented with very conspicuous, sharp, longitudinal ridges, the edges 

 whereof are often serrate, surface of keel showing occasional 

 ridges ; pitting very coarse ; on the whole outer surface the pits 

 have a tendency to be arranged in transverse rows, which are best 

 seen on the keel and ridges. The outline of the seed when viewed 

 from the interior is crested and serrate at the apex and sides ; 

 micropyle subbasal, oblique ; hilum at the base of the dorsal edge ; 

 raphe marginal from the hilum to the middle of the dorsal margin, 

 diagonal thereafter : the curvature of the diagonal portion is so 

 slight that the width of the testa external to the raphe is equal to 

 or greater than the width of testa on its inner side; digitate 

 cells of the interior of the keel straight, with their length parallel 

 to the length of the seed. 



Dimensions. — Length=6"75 mm. ; breadth=3mm. (largest). 

 Length=5"5 mm. ; breadth=3 mm. (smallest). Occasionally 

 pockets occur which contain only stunted or undeveloped specimens, 

 the length of these varying from 5 - 5 to 4 mm. and their breadth 

 from 2*5 to 2 mm. 



Although the seed was doubtless originally somewhat flattened, 

 a certain amount of flattening is due to subsequent pressure, since 

 different examples show compression in different directions. 



Horizon. — Middle Oligocene, Hamstead Beds. 



Localities. — Bouldnor Cliff, Yarmouth (Isle of Wight); 

 Hamstead (Isle of Wight). 



Affinities. — This species is very closely related to S.neglectus, 

 of which it seems to be a somewhat later form. The chief 

 external features in which it differs from that species are the 

 broader keel, the smaller, more irregular, flattened collar, the 

 sharper ribs, and the very coarse pitting. Viewed internally, the 

 apex and sides show a crested serrate outline ; while S. neglectus, 

 when similarly viewed, shows an unbroken outline. The chief 

 internal distinction is seen in the diagonal portion of the raphe ; 

 in S. neglectus this is more curved than in S. acuticostatus, with 

 the result that the part of the keel external to the raphe is usually 

 narrower than the part inside the raphe in S. neglectus, while it 

 is generally wider than the part inside in S. acuticostatus. 



