Dr. A. Smith Woodivard — Notes on Pycnodont Fishes. 387 



In Mesodon, Microdon, Stemmatodus, Gyrodus, and Mesturus, the 

 roof-bones form a continuous shield ; but in Ccelodus, Pycnodus, and 

 perhaps Palceolalistum, there is a small supratemporal vacuity on 

 each side, bounded in front by the frontal, mesially and in part 

 posteriorly by the " supraoccipital ", laterally and in part posteriorly 

 by the " parietal ". In the British Museum this vacuity is well seen 

 in specimens of a new species of Ccelodus from the Lithographic Stone 

 of the Montsech, Lerida, Spain (Nos. P. 10999, 11000), in Ccelodus 

 cost<% from Castellamare, Italy (Nos. P. 1671, 167l«), in the so-called 

 Palceobalistum ponsorti (which is probably a species of Pycnodus) from 

 Mont Aime, Marne, Prance (Nos. 28292, P. 1638), and in Pycnodus 

 platessus (No. P. 1633) and P. gibhosus (No. P. 1634) from Monte Bolca, 

 Italy. It evidently corresponds with the supratemporal vacuity in 

 the existing teleosteans of the family Zeida?, 1 and implies that in the 

 Pycnodont genera just mentioned the lateral muscles of the trunk 

 extended slightly forwards over the cranial roof. The " supra- 

 occipital" is therefore probably the foremost dorsal ridge-scale 

 enlarged and displaced forwards, while the part of the "parietal" 

 bounding the vacuity behind is really a supratemporal. 



The delicate and toothless pterygoid arcade, which was first seen 

 in Anomceodus and Mesturus, has now been observed both in Gyrodus 

 and Ccelodus ; but the nature of the palatine bone remains uncertain. 

 In the tritoral dentition there is still no satisfactory evidence of 

 successional teeth. There are usually only two prehensile teeth in 

 each premaxilla and dentary ; but both in Gyrodus and in Mesturus 

 there are three or four teeth in the premaxilla, four in the dentary. 



Although the dentition is obviously adapted for crushing hard 

 skeletons, it is curious that no example of a Pycnodont has hitherto 

 been described showing the contents of the stomach. There appears 

 to be only one such specimen in the British Museum — a small 

 individual of Pycnodus platessus, shown of the natural size in 

 Plate XXIV. Here the distended stomach is filled with the 

 comminuted remains of bivalved shells, which are ornamented with 

 radiating riblets, but are too imperfect for determination. 



In this connection it is interesting to notice that some of the 

 Pycnodonts agree with the existing Batistes in possessing clusters of 

 small claw-shaped pharyngeal teeth. These teeth, found isolated, 

 are known to paleontologists under the name oiAncistrodus. 2 In the 

 British Museum I first observed them in their natural position in 

 specimens of Ccelodus from the Montsech, Spain (No. P. 10996). They 

 are seen in nearly all specimens of Palceobalistum ponsorti from Mont 

 Aime, Prance, and in Pycnodus platessus from Monte Bolca, Italy 

 (Nos. 41083, P. 4386). They also occur in the type-specimen of 

 Xenopholis carinatus and in a new specimen of the latter species 

 (No. P. 10700). Similar teeth are seen in front of the mandible of 

 a specimen of Xenopholis in the Court Museum, Vienna ; and five 



1 E. C. Starks, "The Osteology and Relationships of the Family Zeidas" : 

 Proc. U.S. Nat. Mus., vol. xxi (1898), p. 471, pi. xxxiii. 



2 W. Dames, " Ueber Ancistrodon" : Zeitschr. deutsch. geol. Ges., 1883, 

 pp. 655-70, pi. xix. See also figure by A. Gaudry, Les Enchainements du 

 Monde Animal. — Fossiles Secondaires (1890), p. 167, fig. 263. 



