62 BULLETIN" 161, UNITED STATES NATIONAL MUSEUM 



A number of the species of this genus have become adapted to a 

 cold, deep-water habitat, an unusual one for most of the genera of 

 this family. 



In the shallow water of the Pacific the genus is often very 

 abundant, but is limited to a very few species. 



PYRGO DENTICULATA (H. B. Brady) 



Plate 14, Figures 1-9 



Biloculina ringens Lamarck var. denticulata H. B. Brady, Rep. Voy. Challenger, 



Zoology, vol. 9, p. 143, pi. 3, figs. 4, 5, 1884. — Woodward, The Observer, vol. 



4, p. 76, 1893.— Millett, Journ. Roy. Micr. Soc, 1898, p. 262.— Chapman, 



Journ. Linn. Soc. Zool., vol. 28, p. 398 (list), 1902.— Dakin, Rep. Pearl 



Oyster Fish. Ceylon, pt. 5, p. 220, 1906. — Heron-Allen and Earland, Trans. 



Zool. Soc. London, vol. 20, pt. 17, p. 551, pi. 40, figs. 11-13, 1915. 

 Biloculina denticulata Cushman, U. S. Nat. Mus. Bull. 71, pt. 6, p. 80, pi. 33, 



fig. 1, 1917 ; U. S. Nat. Mus. Bull. 100, vol. 4, p. 476, pi. 98, figs. 3, a, o, 1921 ; 



Carnegie Inst. Washington Publ. 311, p. 78, 1922; Publ. 342, p. 70, 1924; 



Publ. 344, p. 83, 1926.— Hanzawa, Jap. Journ. Geol. Pal., vol. 4, p. 38, 



(table), 1925 (1926). 

 Pyrgo denticulata Cushman, U. S. Nat. Mus. Bull. 104, pt. 6, p. 69, pi. 18, figs. 



3, 4, 1929. 



Test elongate, roughly quadrangular in front view, in end view 

 somewhat compressed, biconvex, apertural end broadly rounded, 

 opposite end with a series of short, irregular teeth ; wall smooth, us- 

 ually polished; aperture very broad and narrow, extending nearly 

 the whole width of the test, the ends somewhat expanded, with a long, 

 narrow tooth, making the inner border of the aperture platelike, 

 somewhat raised above the level of the surface to which it is attached, 

 as is the whole border of the aperture. Length, 0.6-1 mm. ; breadth, 

 0.45-0.9 mm.; thickness, 0.3-0.5 mm. 



This is a typical species of the Indo-Pacific usually most abundant 

 in coral reef regions. There are numerous records for it from shal- 

 low water in various parts of the Pacific from the Philippines to the 

 Hawaiian Islands, southward through the various groups of islands, 

 and westward to the coast of Africa. It also occurs in much less 

 abundance and is less well developed in the Atlantic. It is by far the 

 most common species of the genus in the material we have examined 

 from the South Pacific. There is a great deal of variation in this 

 species, and some of the various forms are figured here. The young 

 stage is very close to Pyrgo elongata in many ways, and it is these 

 small light forms that are most easily carried out into deep water by 

 the current and are found at a number of Albatross stations a short 

 distance away from these islands, as will be noted. The figures give 

 these early stages, which may be compared with the adults. Not all 



