736 MESSES. E. HEEON-ALLEN AND A. EA ELAND ON THE 



surface," a statement which is borne out by the figure. The general contour of his 

 shell with its inflated chambers and lobate periphery is, however, identical with the 

 Kerimba form, and although the delicate costse in the Kerimba specimens seldom 

 coalesce so as to form a definite network, instances occur in which such is actually 

 the case. 



Breadth 0-3 to 0-5 mm. ; thickness, variable, O'l to 0'2 mm. 



Subfamily N u M M u l i t i N /E. 

 AjMPHIstegina d'Orbigny. 



458. Amphistegina lessonii d'Orbigny. 



jimphistegina lessonii d'Orbigny, 1826, TMC. p. 304. no. 3, pi. xvii. figs. 1-4, Modele no. 98. 

 wtt/^am d'Orbigny, 1826, TMC. p. 305. no. 8, Module no. 40. 

 lessonii Mobiiis, 1880, FM. p. 99, pi. x. figs. 10-14, pi. xi. figs. 1-3. 

 Brady, 1884, FC. p. 740, ])\. cxi. figs. 1-7. 

 Fornasini, 1903, AG. p. 149, pi. ii. fig. 1, 

 Chapman, 1900, FLF. p. 204. 



Millett, 1898, etc., PM. 1904, p. 605 (References). 

 Dakin, 1906, FC. p. 2l0, pi. — . fig. 13. 



15 Stations. 



Occurs at nearly all Stns., very common at some, but nowhere in any of the thin 

 evolute varieties. The most widely distributed variety is the large equally biconvex 

 form {^= Amphistegina lessonii d'Orb.), reaching its best development at Stns. 9 and 11. 

 The plano-convex type {=:■ Amphistegina trilohata d'Orb.) occurs in company with this 

 in most of the dredgings (see F. 1903, AO. p. 143, pi. ii. fig. 3). 



At a few Stns. biconvex specimens without the distinctive beaded markings round 

 the aperture occur. These, which are otheriwse inseparable from the typical 

 A. lessonii, are probably the A. madagasca7-iensis of d'Orbigny, recorded by him from 

 the adjacent island of Madagascar {loo. cit. p. 144, pi. ii. fig. 4). 



459. Amphistegina lessonii, var. radiata (Fichtel & Moll). 



Nautilus radiatus Fichtel & Moll, 1798, TM. p. 58, pi. viii. figs. a-d. 



„ „ (Nummulina) Parker & Jones, 1859, etc., NF. 1860, pp. 105, 106. 



Amphistegina radiata Chapman, 1895, FAS. pp. 45-47, pi. i. figs. 8-10, 12. 



o Stations. 



Some specimens of the large and many-chambered biconvex form, separated by 

 Chapman as referable to Fichtel and Moll's species, accompanied the type at three 

 Stns. They are specially noticeable owing to their smooth surface and the transparent 

 lines in the shell-substance, marking the sutural divisions. 



