XIPHITDJ5. 
491 
Roof of cranium gently and regularly convex, the fossae for the 
forward production of the lateral muscles of the trunk very slightly 
extended over the occipital border ; rostrum rounded in section, and 
each premaxilla traversed by two principal longitudinal nutritive 
canals, one above the other. Teeth minute and clustered. 
This genus is only definitely known by the skull, but typical 
Xiphioid vertebras occur in the same formations as the fossils 
referred to it. 
Xiphiorhynchus elegans, V an Beneden. 
IdiT. Xiphiorhynchus elegans, P. J. Ian Beneden, Bull. Acad. 
Belg. [2] vol. xxxi. p. 499, pi. ii. fig 8 - 3, 4. 
Type. Rostrum ; Abbey of Affligem, Mclle, near Ghent. 
The type species, known only by the rostrum, about 0 2 in length 
b y 0-03 in width at the base, lustrum rather depressed, twice as 
broad as deep near the base. 
Form. $ hoc. Middle Eocene (Bruxellian) : Belgium. 
Xot represented in the Collection. 
Xiphiorhynchus priscus (Agassiz). 
[Plate XIX. figs. 1, 2. Text-figure 18, no. 1.] 
(?) 1829. Chelonia railiata, G. Fischer, Nouv. Mena. Soc. Imp. Nat. 
Moscou, vol. i. p. 297, pi. xx. fig. 2. [Portion of skull ; Geological 
Museum, University of Moscow.] 
1834. Tetraptw'us 1 L. Agassiz, Neues Jahrb. p. 30* *. 
1889-44. Tetrapterus priscus, L. Agassiz, Poiss. Foss. vol. v. pt. l. 
P- 91, pi. xxxi. , „ . „ 
(?) 1851. Ommatolampes eichwaldi, G. Fischer de Waldheim, Omm*- 
tolampes et Trachelacanthus, p. 3, pL i. [= Chelonia raduita , 
1829]. 
1869. Histiophorus priscus, E. D. Cope, Proc. Boston Soc. Nat. Ilist. 
vol. xii. p. 310. 
Type. Imperfect skull ; Museum of Natural History, I aris. 
Rather larger than the type species, with a less depressed rostrum, 
which is al ways more than half as deep as broad. 
In physical characters the type specimen of the so-called Omma- 
tolampeg is identical with the fossils from the London Clay of 
Sheppey. It is said to have been obtained from Siberia, but in the 
original description (1829) the exact locality and circumstances of 
its discovery are stated to be unknown. 
-Form. Loc. Lower Eocene (London Clay): London Basin. 
