70 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
disturbed anteriorly, scarcely at all so posterior to the line of flexure. All] the 
fins with the exception of the pectorals are beautifully preserved, but both 
pectorals are very defective. Notwithstanding the thickness of its separate 
plates, the cranial box yielded to pressure of the overlying matrix, and became 
irregularly flattened prior to fossilization. Most of the external head-bones are 
displaced, and the only ones escaping serious injury are the opercular apparatus 
and jaws of the right-hand side. The cranium, therefore, is in a very unsatis- 
factory condition for study, and it is fortunate our knowledge of its osteology 
is supplemented by a second specimen, which is described below. 
Cranwm, — Turning our attention first to the right-hand side of the head, 
we find that the operculum, suboperculum, interoperculum, preorbitals, maxil- 
lary and mandibular ramus all occupy their normal position with respect to 
one another, being simply flattened out, not displaced. The opercular plates 
have practically the same configuration and arrangement as in recent species, 
but are many times more massive, thus harmonizing with the powerful armor- 
ing of the trunk. The postero-inferior angle of the interoperculum is developed 
into a stout, blunt process overlapping the suboperculum. The latter plate, 
together with the operculum, has a slightly different ornamentation from the 
remaining bones of the head, in that the ganoine tubercles are fused into 
more or less continuous and radiating ridges. On the jaws and bones form- 
ing the roof of the head the tubercular ridges are ramifying and irregularly 
confluent, 
The maxillary is preserved in its entirety and measures 19 cm. in length. 
Anteriorly it shows a fontanelle as in recent forms, but traces of its segmenta- 
tion are now nearly obliterated. In the Washington cranium described by 
Mr. Lucas the segments are very distinct, and are seven in number. (See 
infra, p. 73). As the oral aspect of the maxillary is not exposed, nothing can 
be affirmed of its dentition. Considering its extreme narrowness, however, 
and the fact that only a single dental groove is opposed to it in the lower jaw, 
it is improbable that more than one series of large teeth was present. In this 
character a noteworthy difference is to be observed between the species under 
consideration and the recent L. tristechus (= L. viridis Gthr.), with which it 
stands otherwise in close agreement ; and incidentally it proves the artificial 
nature of Rafinesque’s subgenus Atractosteus. For if we emend the definition 
of the latter so as to include its nearest allied fossil species, no characters are 
left by which it can be distinguished from Lepidosteus s. str. Hence it seems 
best to discard altogether the subgeneric terms Atractosteus and Cylindrosteus.! 
The mandibular ramus is 25 em. long and composed of the usual parts, den- 
tary, angular, and coronoid. Immediately behind the last-named element are 
two circumorbital plates, but all the remaining circumorbitals and suborbitals 
1 According to Jordan and Evermann (Bull. 47, U. S. Nat. Mus., pt. 1, p. 109), 
“The name Litholepis, Rafinesque, applied by him to a gigantic gar, Litholepis ada- 
mantinus, the ‘Devil-jack Diamond Fish, is based on a drawing by Audubon, not 
intended by Audubon to represent any possible fish.” 
