44 Mr. J. W. Jackson on Lusttanian 
M. truncata, though some, such as the double cardinal area 
(7. e., a dorsal as well as a ventral area), do not appear to have 
been emphasized hitherto*. ‘lhomson t+ has recently called 
attention to the fact that in Mihlfeldtia the foramen is shared 
by both valves, the greater portion being in the ventral valve. 
For this position of the foramen he applied the term Amphi- 
thyrid, which has since been altered to Symbolothyrid as 
being more accurate f. 
M. truncata is widely distributed in the Mediterranean 
from Gibraltar to the Augean and on the Atlantic coast from 
the English Channel to the Canaries. It is also recorded 
as a fossil in the Mediterranean region :—Morea (Miocene ?), 
Malta (Miocene), 8. Italy and Sicily (Lower Pliocene and 
later), N. Italy (Lower Pliocene), Provence (Pliocene), and 
Sardinia (Pliocene). Fischer and Oehlert (op. ctt. p. 91) 
cite from the Lower Pliocene of Sicily and Calabria (ex 
Seguenza) a var. granulata, which they believe may be more 
nearly related to the recent M. echinata, only known at 
present from off Cape Bojador, West Africa. The var. 
serravallensis, Sacco §, from the Middle Miocene of N. Italy, 
may be also referable to the same. MM. truncata has been 
recorded from the Miocene of the Vienna Basin and of North 
Italy, but the form in question is now regarded as distinct 
and appertaining to MJ. oblita, Michelotti, probably a smooth 
ancestral species ||. 
The most interesting record for J, truncata outside the 
Mediterranean—Hast Atlantic region is that of Deshayes J] for 
the Island of Réunion, A single example was found here on 
a crustacean dredged at 200 fath., and was described under 
the name of Morrisia gigantea by Deshayes. Judging from 
illustrations it is obviously a small form of MM. truncata**, 
differing only in the scanty nature of the striz. In this 
respect it closely resembles the Persian Gulf variety described 
* This double cardinal area is present in Megathyris decollata; a 
distinct ventral area and a slight dorsal one are present also in Araussina 
rubra, 
+ Thomson, ‘ Brachiopoda Australian Antarctic Expedition, 1911-14,’ 
 Scientitic Reports, ser. C, vol. iv. pt. 8, 1918, p. 20. 
{ Trans. New Zealand Institute, vol. li. 1919, p. 452 (footnote). 
§ Sacco, op. cit. p. 28, pl. v. figs. 52, 53. 
|| Fischer and Oehlert, op. cit. pp. 865-86. 
4] Deshayes, Cat. des Moll. de I’lle de la Réunion (Bourbon), 1863, 
p- 37 (reprint), pl. v. figs. 9, 10, 11. 
** Fischer and Oeblert (op. cit. p. 84) have evidently taken Deshayes’ 
enlarged figures (pl. v. figs. 9, 10) as Tepresenting the natural size, 
having overlooked the dimensions given in the text, 
