THE BRITISH FOSSIL BRACHIOPODA. 



367 



large valve. Prom this definition it appears clearly in what essential points this sub- 

 family deviates from the Thecideina. Yet I think these forms ought to be retained in 

 the family Thecideida, as the most striking characters of family, — the punctate shell, the 

 lobed brachial apparatus, and the attached larger valve persist, though under such very 

 strange modifications. There are two genera which I comprise in the sub-family, the 

 genus Lyttonia, Waagen, and the genus Oldhamina, Waagen." 



" The genus Lyttonia, so far as known, is exclusively of eastern distribution. Two 

 species of it occur in the Salt Range as well as in the Himalayas ; a third species has been 

 described by Kayser as a fish tooth under the name of 

 Leptodus Mchthofeni} from the Upper-Carboniferous beds 

 of Lo-Ping in China." I am, however, uncertain whether 

 the L. Richthofeni of Kayser is really a Brachiopod. 

 Prof. Lindstrom writes me that he is convinced that it is so, 

 and that it belongs to the family Productida and is nearest 

 akin to Strophalo&ia. Dr. Waagen says (p. 403) that 

 specimens of the genus Oldhamina " have been long 

 known, but they have always been considered as univalve, 

 and were in consequence compared by L. de Koninck to 

 Bellerophon." 2 "The shell," adds Waagen, (p. 404) "is 

 composed of two valves, one smaller and one larger, corre- 

 ponding respectively to the dorsal and ventral valves of the 

 Brachiopoda. The ventral valve is much more solid, com- 

 pact, and externally entirely smooth, only covered by 

 tolerably numerous concentric strise of growth. It is 



at the same time very strongly vaulted, nearly hemispherical, and strongly bent over 

 in the apical region. In consequence of this the hinge-line is not visible, being covered 

 up by a thick callosity, which envelops the apical part of the valve and extends on 



both sides in wing-like expansions, rolled up spirally The dorsal valve is 



constructed very much as in Lytto?iia. It is strongly concave, and consists of a longi- 

 tudinal solid middle piece, to which are attached laterally long narrow shelly lobes, 

 separated from each other by deep narrow incisions, into which fit the lateral septa 

 of the ventral valve." 



We have long known that in some species of Thecidium, such as Th. leptanoides, 

 Deslongchamps, Th. 3/ayaIis, Desl., 3 and Th. Buuchardi, Dav., the dorsal valve does 

 not attain to much more than half or two-thirds the length of the ventral valve, so 



Oldhamina decipiens (after Waageu). 



A. Ventral valve, internal view. 



B. Cardinal view of the dorsal valve. 



1 "Leptodus "Richthofeni" Kayser, in Richthofen's 'China,' vol. iv, p, 161, pi. xxi, figs. 9 — 11, 1882. 



2 De Koninck, 'Quart. Journal Geol. Soc.,' London, vol. xix, p. 8, 1863, and ' Fossiles Paleoziques 

 de l'lnde,' p. 15, 1863. 



3 " Sur les genres Leptsena et Thecidea des Terrains Jurassiques du Calvados," ' Memoires de la Soc. 

 Linn6enne de Normandie,' vol. ix, 1853 ; see also my Jurassic Supplement, PI. XIII, fig. 1. 



