210 A. Smith Woodward — Greensand Ganoid Fishes. 



This form of splenial dentition most nearly resembles that of 

 A. angustus, but is distinguished by the form and proportions 

 of the flanking teeth. 



Family EUGNATHID^. 

 Genus Lophiostomus. 



This genus has hitherto been found only in the Chalk, and but 

 a single example of the skull is known. It is thus of great interest 

 to record the discovery of two fragments of the cranium in the 

 Cambridge Greensand, which evidently pertain to a new species. 



Lophiostomus affinis, sp. nov. PI. VIII, Figs. 6, 6a. 



Type. Occipital half of cranial roof: Brit. Mas. (Jesson Collection). 



As shown by the figures which represent the upper and right 

 lateral aspects, the imperfect fossil on which this species is founded 

 indicates a skull of similar form and proportions to that of the 

 typical L. Dixoni. The superficial ornament, however, consists of 

 finer elongated tubercles ; while the frontal prominence (p.) on 

 either side is very slightly elevated compared with that of the 

 typical species. The occipital border is preserved, showing a broad 

 smooth surface of overlap (o.) ; and this border is not straight but 

 somewhat excavated by a re-entering angle. No certain indications 

 of sutures between the component elements can be observed. 



The second specimen, in the Woodwardian Museum, Cambridge, 

 shows exactly the same portion of the cranial roof with identical 

 characters, but is also interesting as preserving the occipital region. 

 As in the preceding specimen, there is no trace of a prominence on 

 the squamosal, such as appears to be present on the right side of 

 the only known skull of L. Dixoni. The cartilages of the occipital 

 and otic regions are well ossified, and there is a deep conical fossa 

 in the articular face of the basioccipital. There are indications of 

 a deeply jagged median suture between the frontal bones, but 

 otherwise the limits of all elements are indistinguishable. 



Family ASPIDORHTNCHID^. 

 Genus Belonostomus, Agassiz. 



This genus is represented in the Cambridge Greensand not only 

 by fragments of the characteristic presymphysial bone, but also 

 by portions of the skull and scales. Two imperfect scales in the 

 Woodwardian Museum are as large as those of the Australian 

 species, B. Sioeeti, and similarly ornamented ; while the portions of 

 skulls are of two kinds, one equally large, the other comparatively 

 small and depressed. 



Only the hinder half of the skull is preserved in each case. Of 

 the lai-ger form there are four examples in the Jesson Collection 

 (Brit. Mus. No. P. 7235), measuring from 004m. to 0-05 m. across 

 the post-frontal region, and all exhibiting the robust ossification of 

 the otic elements. The basisphenoidal region is much laterally 

 compressed, but no sutures can be observed between any of the 



