434 Dr. A. Gunther — Tertiary Fishes of Sumatra. 



that the specimens representing this class of animals in Museums are 

 unsuitable for thorough comparison with allied extinct forms, being 

 generally young and of small size. Sumatra offers, for many years 

 to come, a rich field to the Zoologist as well as Geologist.^ 



The following table will show at a glance the geographical 

 distribution in recent times of the fossil Sumatran genera described 

 in this paper : — 



1. Auliscops. 1 species is known from N.W. America. 



2. Pseudeutropius. Several sp. from the Continent of India and Sumatra. 



3. Bagarius. 1 sp. from the Continent of India and Java. 



4. Thynnichthys. 2 sp. from the Continent of India and 2 from Sumatra. 



5. Barbiis. Numerous species all over India. 



6. Amhlypharyngodon. 3 sp. from the Continent of India. 



7. Hexapsephus. Known from Sumatran fossil only. 



8. Notopterus. Several species from the Continent and Sumatra. 



9. Chirocentrus. 1 sp. from the Indian Ocean. 



I. — Fossils fkom the Marl-slates. 

 Auliscops sumatranus. (PI. XV. Fig. 1.) 



One species only of this genus has hitherto been known. It occurs 

 on the north-west coast of America, and has been found in salt- 

 water ; however, it is a well-ascertained fact that the species of 

 GastrosteidcB, to which Auliscops is allied, readily change their 

 habitat from fresh- to brackish- and even salt-water, and vice versa. 

 Fistularia likewise enters fresh-water. As far as the characters of 

 the genus Auliscops are known, there appears to be no reason why 

 the Sumatran fossils before us should not be referred to it. 



The snout is comparatively short ; the centres of the vertebrse 

 are not grooved on their abdominal surface, as in Fistularia and 

 Aulostoma ; the dorsal and anal fins are short ; the caudal is rounded, 

 without prolonged central ray ; there is a series of anterior dorsal 

 spines ; the interneurals are horizontally situated, forming together 

 one continuous bony strip ; and there are no external pubic shields.^ 



Five specimens of this fish are in the collection. 



a. The largest is 14^ inches long, showing scarcely more than 

 the general outline of the fish. The interneural stri^D is well shown, 

 likewise the number of the neural spines, but the centres of the 

 vertebrae of the abdominal portion are destroyed. 



h. This specimen (which is figured) is 11 inches long, and is 



1 The manuscript of this paper had been delivered to the Editor, when Mr. 

 Griesbach drew my attention to a paper on " Fossile Fische von Sumatra" by Dr. 

 W. V. d. Marck, Palseontograph. 1876, April, pp. 405-414, pis. 23 and 24. As the 

 materials in the British Museum were much richer than those at the disposal of that 

 author, I had nothing to alter in my manuscript, with the exception of the specific 

 name of the most common fish of this formation, viz. Thynnichthys amblyostoma. 

 Through Dr. v. d. Marck's paper I became acquainted with Prof. Eiitimeyer's 

 *' Bemerkungen zu den fossilen Fischen von Sumatra " (Abhandl. Schweiz. palseont. 

 Ges. i. 1874). To judge from his description, I think that the fish named " Smerdis " 

 by him, will prove to be an Ambnssis, a genus very common in the fresh-waters of 

 the Indian region. The so-called Dussumierina appears to me to be fry, and, at 

 present, indeterminable. 



2 We may remark here that the skeleton figured by Agassiz, in Poiss. foss. vol. iv. 

 tab. XXXV. fig. i., under the name of Aulostoma chinense, is not that species or even 

 genus, but Fistularia tabaccaria. 



