370 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Genus AMPfflSTEGINA d'Orbigny, 1826. 



A reference to the various figures and, descriptions given by Brady 

 and by the subsequent authors will show that the genus Amphiste- 

 gina includes numerous things. Brady refers all the forms of the 

 genus to AmpMsiegina lessonii. Heron-Allen and Earland in their 

 Kerimba paper reference (p. 736) distinguish three forms and mention 

 a fourth. Fornasini ^^ has given figures of the various forms from 

 the Planches In§dites of d'Orbigny. A study of the Philippine 

 material, which is abundant, has shown several forms which seem 

 to be distinct. A comparison of these with the originals of d'Orbigny 

 shows several interesting points. The original figures of d'Orbigny^* 

 show a form nearly equally biconvex, with a blunt periphery and 

 very numerous chambers, usually with a secondary series of clear 

 shell tissue between the suture lines. D'Orbigny's model, however 

 (No. 98), shows a more convex form with an acutely carinate 

 periphery and much fewer chambers. This form is close to that figured 

 by Fornasini (pi. 2, fig. 1). If from these two distinct forms which 

 d'Orbigny had under this name the original of the figure in the 1826 

 work is taken as a type, the typical A. lessonii as considered here 

 will be a rather flattened biconvex test with a bluntly rounded 

 periphery, very numerous narrow oblique chambers, and with the umbo 

 very small but prominent, usually clear shell material. The sutures 

 are almost always darker than the rest of the test, and between them 

 are usually shorter lines or points, also clear shell material, showing 

 dark against the lighter colored background. The second form, 

 which in Fornasini's paper is figured (pi. 2, fig.), represents a variety 

 named by d'Orbigny madagascariensis. This has few chambers, an 

 acutely carinate border, very oblique sutures, and no papillae near 

 the umbilical area. These two forms are very distinct in the Philip- 

 pine specimens. A third very large form has very numerous cham- 

 bers, the sutures nearly straight, and radiating from the center to 

 the periphery. This is the form distinguished by Chapman and 

 Heron- Allen and Earland as variety radiata (Fichtel and Moll). 



The genus is most common in shallow, warm water, especially 

 among the islands of the Archipelago. 



AMPHISTEGINA LESSONII d'Orbigny. 



Amphistegina lessonii d'Oebigny, Ann. Sci. Nat., vol. 7, 1826, p. 304, No. 3, pi. 

 17, figs. 1-^.— H. B. Brady, Rep. Voy. Challenger, Zoology, vol. 9, 1884, p. 

 740, pi. Ill, fig. 1.— CusHMAN, Bull. 71, U. S. Nat. Mus., pt. 4, 1914, p. 35. 



The typical form of the species, as has already been noted, is a 

 biconvex test with very numerous oblique chambers, the periphery 

 bluntly rounded, the sutures oblique, very sharply angled near the 

 periphery; the sutures themselves on the surface usually all clear 

 shell material, showing darker against the nearly white opaque back- 

 ground formed by the lateral walls of the chamber; also between the 

 sutures there are shorter lines of clear shell material and very often 



» Rend. Acad. Sci. Bologna, vol. 7, 1903. » Ann. Sci. Nat., vol. 7, 1826, pi. 17, figs. 1-4. 



