542 Herbert A. Baker — Unconformity between 



of the ganoids from the Bavarian Lithographic Stone, Asthenocormus 

 \_Agassizia~\ titanius} 



Assuming that Buckland's determination of the coprolites of 

 Ichthyosaurus wits correct, Gaudry 2 seems to have been the first 

 to ascribe similar coprolites to a Labyrinth odont. He was then 

 followed by von Amnion 3 and Neumayer.* In these cases again, 

 however, the coprolites and skeletons were merely found in the same 

 stratum, the one fossil never actually within the other. Though 

 coprolitic matter is sometimes seen in the common Archegosaurus 

 and other genera, it has never been observed to exhibit the spiral 

 impression. Indeed, the only Labyrinthodont — a small Branchio- 

 saurian — in which the whole course of the alimentary canal has been 

 clearly distinguished, agrees in its digestive arrangements with an 

 ordinary salamander. 5 Fritsch was therefore probably right when 

 he concluded 6 that the coprolites bearing marks of a spiral valve, 

 found in the same strata as the Lahyrinthodonts, could scarcely 

 belong to these animals, hut must rather be referred to the associated 

 selachian and ganoid fishes. 



There is tbus no reason for helieving that either the earliest 

 Amphibians or the earliest Reptiles retained the peculiar structure 

 of the intestine which characterized the ancestral Fishes. 



EXPLANATION OF PLATE XXXIV. 



Ventral view of a shark (Cladoselctche clarki) from the Upper Devonian of Berea, 

 Ohio, U.S.A., showing the intestine (int.) with a spiral valve, filled with 

 partially digested food ; one-sixth nat. size. British Museum, No. P. 9271. 



III. — On the Unconformity between the Cretaceous and Older 



Bocks in East Kent. 7 



By Herbert Arthur Baker, B.Sc, F.G.S. 



(WITH TWO MAPS AND SECTION IN TEXT.) 



IN a previous paper 8 the writer briefly alluded to the evidence, as 

 known from the deep borings in East Kent, afforded by tbe 

 Palaeozoic and Mesozoic rocks, of the operation of a posthumous 



1 B. Vetter, Mittheil. k. mineral. -geol. Mus. Dresden, pt. iv, p. 105, 1881 ; 

 C. R. Eastman, Mem. Carnegie Mus., vol. vi, p. 416, 1914. 



2 A. Gaudry, " L'Aetinodon " : Nouv. Archiv. Mus. d'Hist. Nat. Paris, 

 ser. II, vol. x, p. 19, text-fig. 8, 1887. 



3 L. von Ammon, Die permischen Amphibien der Bheinpfalz, p. 102, pi. iv, 

 fig. 4 (Munich, 1889). 



4 L. Neumayer, "Die Koprolithen des Perms von Texas": Palceonto- 

 graphica, vol. li, pp. 121-8, pi. xiv, 1904. 



5 B. L. Moodie, " The Alimentary Canal of a Carboniferous Salamander" : 

 Amer. Nat., vol. xliv, pp. 367-75, with figs., 1910 ; also The Coal Measures 

 Amphibia of North America, pp. 26, 59, figs. 7, 14, Carnegie Institution, 1916. 



6 A. Fritsch, Fauna der Gaskohle, etc., vol. ii, p. 59, 1885. 



7 [This article and its illustrations were sent by tbe author to the GEOLOGICAL 

 Magazine on September 27, 1917, and set up in type on October 9, but 

 publication was deferred through want of space until this month. '1 he author 

 has sent a brief note, dated, at sea, November 14, which has been inserted at 

 the end of his paper (see p. 549). — Ed.] 



8 Geol. Mag., Dec. VI, Vol. IV, No. 639, September, 1917, pp. 398-403. 



