510 FUNAFUTI ATOLL. 



for the young of a Spondylus, hence the erroneous statement on 

 p. 402, that the Brachiopoda were absent from the Archipelago. 



The genus Thecidea dates back from the opening of the Mesozoic, 

 and is manifested in numerous species through a long range of 

 formations. Like Nautilus and Trigonia, it now only survives in 

 a few rare and restricted species. It is an interesting coincidence 

 that a genus so intimately associated with fossil coral reefs in 

 Europe, should recur alive on a Pacific Atoll. So far but two recent 

 species, T. mediterranea, Risso, and T. barretti, Woodward, have 

 been detected. The former, for which the subgenus Lacazella has 

 been proposed by Munier Chalmas, is unlike the Pacific species ; 

 whereas the latter and the West Indian T. barretti are quite 

 close. These conform neither to Thecidea, as restricted by Hall 

 and Clarke,* nor to the various subgenera admitted by them. 

 That generic term has been here used in the wider application of 

 Davidson. 



On comparing examples of T. maxilla with the published 

 accounts of T, barretti, I conclude that the characters are so 

 variable that a large series of each will be necessary to discriminate 

 properly between them. At present I would point to the flanges 

 of the median septum and to the greater development of the 

 brachial lamellse, as features possessed by T. maxilla but not 

 by T. barretti.^ The former, indeed, reminds one of a split 

 walnut. 



I am in doubt whether a pseudo-deltidium exists in T. barretti, 

 for Davidson writes J that " in external shape it cannot be 

 distinguished from the Mediterranean species," which has the 

 pseudo-deltidium ; and in a small drawing he indicates the 

 pseudo-deltidium. But, on the other hand, in the enlarged draw- 

 ing, || on which I place more reliance, it is not depicted. Again, 

 it is not shown in his first illustration,U nor is it mentioned in 

 either description. Should a pseudo-deltidium be absent in T. 

 barretti, as it certainly is in T. maxilla, that would isolate these 

 two from the remainder of the genus. 



Another feature in common is the fork which projects in two 

 slender prongs between the cardinal teeth in both species, and 

 strikingly differs from the spoon-shaped processes of T. medi- 

 terranea and from the three prongs of T. radiata, the type of the 

 genus. 



* Hall and Clarke- 47th Ann. Report New York State Mus., 1894, 

 pp. 1091 - 1093. 



t Call Bull. Mus. Comp. Zool., xii., 1886, pi. vi., fig. 2. 

 j Davidson Trans. Linn. Soc., Zool. (2), iv., 1889, p. 162. 

 Davidson Loc. cit., pi. xxiii., fig. 9a. 

 || Davidson Loc. cit., pi. xxiii., fig. 10. 

 IF Davidson Geol. Mag., i., 1864, pi. ii., fig. la. 



