PT'CN'ODONTlDiE. 
221 
formable with the vertical flank-series, are observed at 
the base of the lobe of the pectoral fin; while those of 
the gular and branchiostegal region have already been 
noticed. Haberlein Coll. 
Mesturus leedsi, sp. nov. 
Type. Impea^ct head and trunk ; collection of Alfred H. Leeds, 
Esq., Eyebury. 
A larger species than M. verrucosus , with more coarseH and 
sparsely tubereulated scales, which do not exhibit any radiating 
lines. Ho enlarged tubercles on the course of the lateral line. 
Premaxilla with three, dentary with four prehensile teeth. Vome¬ 
rine and splenial teeth smooth, exhibiting a shallow apical indenta¬ 
tion with a crimped margin, very rarely also with a slight median 
tubercle ; shape of indentation varying with that of the tooth, and 
the hinder portion of its crimped border not infrequently wanting. 
Oral surface of vomer flat, with outer lateral teeth not much 
inferior in size to those of the median series ; inner lateral teeth 
less than half as large as these, very irregular and much supple¬ 
mented behind. Splenial dentition comprising one principal longi¬ 
tudinal series of teeth, all oval and about as large as the median 
vomerine teeth, but with long axis oblique; outermost series 
regular and similar, but rather smaller; one regular row of round 
teeth about half as large, and an innermost irregular row of still 
smaller teeth, within the principal series ; two similar rows of 
small teeth also interposed between the latter and the outermost 
series, but these again irregularly supplemented in the hinder two- 
thirds of the bone. 
Form. Sf Loc. Oxfordian : Huntingdonshire. 
P. 6834. Associated series of bones isolated from matrix; Oxford 
Clay, near Peterborough. In the nomenclature here 
adopted the series comprises the parasphenoid, basi- 
sphenoid, right postfrontal, right and left squamosal, 
portion of right frontal, right and left operculum, and 
other fragments. Leeds Coll. 
1 i<u(» £XW ^* , 
Genus MI^RODON, Agassiz b KWjU. 1 1 j ^ * 
[Poiss. Eoss. vol. ii. pfiT i. 1833, p. 16, pt. ii. 1844, p. 204.] 
Trunk deeply fusiform, often almost discoidal, with a slender 
abbreviated caudal pedicle. Head and opercular bones ornamented 
1 This name having gained universal acceptance, we adopt it, notwithstanding 
its preoccupation among Diptera by Microdon, Meigen, 1803. 
