1895.] POEAMISrirERA FEOM the ARABIAIf SEA. 47 



transverse sections of the tests (see fig. 12). In all cases those 

 observed consisted of two chambers, and they are exactly com- 

 parable in shape with the early chambers of the adult specimens, 

 which, by the way, belong to the inegalospheric type of growth. 



In a paper on " h' Ampliistefjina del calcare lenticolare di Par- 

 lascio " \ Dr. G. A. de Amicis described a form of Amphister/iaa 

 formerly named JS'iinvnulU^'s targionii by Professor Meneghini, bat 

 which is shown by Dr. de Amicis to be a true Amphisiegina. 

 It appears to approach very closely in its general characters to 

 A. radiata, which it especially resembles in the subdivision of 

 the peripheral margins of the successive layers seen in ti'ansverse 

 section '-. 



The specimens of A. radiata found in the Arabian Sea avei'age 

 g of an inch in diameter, and are thus somewhat larger than the 

 speciuiens originally described by Fichtel and Moll. The usual 

 number of principal septa appearing on the surface of full-grown 

 individuals is from eighteen to twenty, and these septa often show 

 a tendency to bifurcate to\\ards the periphery. The surface of 

 the test is tolerably smooth, and the septal lines are marked out in 

 clear transparent sheU-matter, while the rest of the test is of a 

 creamy- white colour. 



Incidentally I may mention that although the form which has 

 been referred to as JS'ummulina ciiminyii by Drs. Carjjenter and 

 Brady has not occurred in these deposits, I have no doubt that, 

 as Professor Eupert Jones has already suggested to me, that 

 species is more properly referable to the " Nautilus venosas " of 

 Pichtel and Moll, and should perhaps stand as Nummidina venosa 

 (F. & M.). It is open to some question, however, whether it is 

 a truly Xummuline form, since some published drawings of the 

 species show a decidedly inequilateral growth, and in point of fact 

 a series of specimens may show all gradations into Operculina. 



Amphistegina radiata was found only in Sample Xo. 2, in which 

 it was common. 



Opebccxina, d'Orbigny. 



274. Operculisa complakata (Defrance). 



Lenticidites complamita, Defrance, 1822, Diet. Sci. Nat. vol. xxv. 

 p. 453. 



Opjerculina aralica. Carter, 1853, Journ. Eoy. Asiatic Soc, 

 Bombay Branch, vol. iv. p. 437, pi. xviii. 



Opercidina complanata, Brady, 1884, Chall. Eep. vol. ix. p. 743, 

 pi. cxii. figs. 3-5, 8. 



The above species was described under the name of 0. arahica 

 by H. J. Carter, who obtained his specimens off the south-east 

 coast of Arabia. 



Found in Sample No. 1, fi-equent. 



' 1885. Process! verbal! delta Societa Toscana di Scienze Naturali. 

 ■^ See also De Amicis, 1886, " It Calcare ad Amphiategma nella Provincia di 

 Pisa," AtLi Soc. Toscar.a Sci. Xat., Memorie, vol. vii. pi. xi. figs. 1, 3, 0, 7. 



