38 



WEALDEN AND PURBECK FOSSIL FISHES. 



tlio brain-case, as in tlie salmon (PI. X, fig. 1 a, e.vo.). A large oval foramen for 

 the exit of the vagus nerve (x) is conspicuous in this lateral face. The lower 

 limit of the exoccipital is not seen in the fossil represented in PI. X, figs. 1, 1 a, 

 owino- to the water-worn condition of the basioccipital (Ao.). of which only the 

 \ii)per part, forming the roof of the notochordal cavity, is preserved. Its upper 

 limit is also obscure laterally, but it appears to be capped by a small opisthotic 

 (opo.), which forms the floor of the diminutive temporal fossa, and unites inside 

 with a Intcral prominence of the epiotic. The exoccipital and opisthotic are 

 suturally united in front with a large pro-otic element (pro.), which doubtless 

 meets the epiotic postero-superiorly, and is cap|)ed ])y a small sphenotic (or post- 



FlG. 15. — Lepidotus sp.; ocoipital portion of skull, li-ft lateral (A), posterior (B), and superior (C) 

 views, nat. size. — Oxford Clay; Peterborough. Leeds Collection (B. M. no. P. 9998). ho., basi- 

 occipital ; epo., epiotic ; ea?o., exoccipital ; f.m., foramen magnum, reduced by distortion : hy.. hypo- 

 centrum of first vertebra ; ?i., pit in basioccipital for notochord ; pL, phnirocentrum of first vertebra : 

 !■., process of epiotic, nature undetermined; r., facet on hypocentrum for articulation of rib; x., 

 faeet probably for opisthotic. 



frontal) antero-superiorly. The sphenotic is not clearly seen in the original of 

 PI. X, fig. 1 a, but is partly shown in another specimen in the British Museum 

 (no. P. 6342). 



It is interesting to note that a similar arrangement of the epiotic bones in the 

 occiput has been discovered by Mr. Alfred X. Leeds in a skull of Lepidotns from 

 the Oxford Clay of Peterborough (Brit. Mus., no. P. 9998). The various elements 

 are somewhat crushed and broken (Text-fig. 15), but the epiotics (epo.) are com- 

 plete, and can be handled separately, proving that they meet in the middle line 

 not only behind but above the brain-cavity throughout their entire length. They 

 rest directly on the exoccipitals (e.ro.), which are fractured behind and so much 

 crushed as almost to obscure the foramen magnum {f.m.). The exoccipital extends 



