502 MB. A. SMITH WOOUWAnD ON EXTINCT [Mar. 17, 



directed process. The left maxilla (ma;.) is completely preserved, 

 slightly arched in form, with a small ascending process near its 

 anterior end, and a little expansion posteriorly. Of the right 

 maxilla only a fragment of the anterior end remains. The pre- 

 maxilloB are not shown, but the bone labelled "? barbel axis" in 

 Cope's original specimen may be one of them. No teeth are 

 exhibited in any part of llie mouth. The preoperculum ip.op.) 

 has a large lower limb and is much expanded at the angle. The 

 operculum {op.) is imperfect, above, but evidently trapezoidal in 

 form aud somewhat deeper than broad. The suboperculum {s.o]).) 

 is deeper behind than in front, and exhibits four deep clefts in the 

 lower half of its hinder border. Small scales can be observed 

 enveloping all the head and opercular bones. 



The vertebral centra are much constricted and strengthened 

 with small irregular longitudinal ridges. The ribs are remarkably 

 slender, apparently supported by stout processes from the centra ; 

 while the separate neural spines in the anterior half of the 

 abdominal region are expanded into thin narrow lamince. The 

 last vertebra of the tail (PI. XVIII. fig. 2) bears an upwardly-turned 

 double style, and there are seven expanded liajmal arches at tiie 

 base of the caudal lin, the lowest apparently connected with the 

 penultimate vertebral centrum, the next three with the last 

 centrum, and the upper three with the terminal style. It is also 

 worthy of note that the neural arch in the three vertebriB pre- 

 ceding the last is forked from the base. Intermuscular bones are 

 seen above the vertebral column throughout, and below it in the 

 caudal region. 



The fins are as described by Cope, exce])t that the pelvic pair is 

 much larger than indicated in the original specimens. The scales 

 are precisely similar in shape and denticulation to those of the 

 existing GonorliyncTius. 



2. NoTOGONEUs 6QUAM0SSEUS. (Plate XYIII. ligs. 3, 4.) 



1818. Oyprinus squamossem, 11. D. de Blainville, Nouv. Diet, 

 d'llist. Nat. vol. xxvii. p. 371. 



1844. SpJunolepis squamosseus, L. Agassiz, Poiss. Foss. vol. v. 

 pt. i. p. 13, pt. ii. p. 87, pi. xlv. 



Formation and Locality. Upper Eocene ; Aix-en-Provenee,rrance. 



The so-called Cyprinus or Sphaiolcpis squamosseus is represented 

 in the British Museum by several siieciniens, which, taken togetlier, 

 display nearly all its essential characters. The head with opercular 

 apparatus is relatively much larger than in Notoc/oneus osculus, its 

 length exceeding the maximum depth of the trunk, aud contained 

 only about four times in the total length of the fish; the vertebral 

 centra are also much shorter ; otherwise its specific characters seem 

 to be identical with those of the American fish. 



The best-preserved head belongs to a specimen wanting part of 

 the abdominal region and the caudal fin, and is shown of two- 

 thirds the natural size in PI. XVIII. fig. 3. It is unfortunately 

 very imperfect, but the enveloping small scales (s.) are exposed 

 in a narrow band, both above and below. The much-fractured 



