68 BULLETIN 10 4, UNITED STATES NATIONAL MUSEUM 



exterior of the test composed of but two chambers; apertm-e typi- 

 cally with a broad bifid tooth. 



Lias to Recent. 



In its microspheric form this genus shows all three stages — quin- 

 queloculine, triloculine, and biloculine — but in the specimens with a 

 small megalospheric proloculum acceleration takes place and the quin- 

 queloculine stage is skipped, and in specimens with a very large 

 proloculum the biloculine character is taken on at once and both the 

 quinqueloculine and triloculine stages are skipped entirely. 



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. 



PYRGO SUBSPHAERICA (d'Orbigny) 



Plate 18, Figures 1, 2 



Biloculina subsphaerica d'Orbigny, in De la Sagra, Hist. Fis. Pol. Nat. Cuba, 

 1839, "Foraminiferes," p. 162, pi. 8, figs. 25-27.— Cushman, Proc. U. S. 

 Nat. Mus., vol. 59, 1921, p. 73; Publ. 311, Carnegie Instit. Washington, 

 1922, p. 77; Publ. 344, 1926, p. S3. 



Test small, rotund, slightly longer than broad, somewhat broader 

 than thick, chambers rounded, periphery rounded; suture distinct, 

 depressed, in side view showing a sinuous line concave toward the 

 last-formed chamber near the aperture and concave toward the pre- 

 ceding chamber at the opposite end; wall smooth and polished; 

 aperture broadly oval with a somewhat flattened tooth with short 

 lateral extensions at the tip only partially filling the aperture. 



Length, 0.50 mm.; breadth, 0.40 mm.; thickness, 0.35 mm. 



This is a characteristic West Indian species originally described 

 from this region by d'Orbigny. It has proved to be the most common 

 species of the genus in this region. I have had it from Jamaica, Cuba, 

 Porto Rico, the Tortugas region, and from numerous stations along 

 the Florida coast and in the Bahamas. It never attains a large size. 



PYRGO MILLETTII (Cushman)? 



Plate 19, Figure 1 



Milioli7ia durrandii Millett (part), Journ. Roy. Micr. Soc, 1898, p. 268, 



pi. 6, figs. 8-10 (not fig. 7). 

 Bilocidina milleUii Cushman, Bull. 71, U. S. Nat. Mus., pt. 6, 1917, p. 81, 



pi. 34, figs. 4, 5; Publ. 311, Carnegie Instit. Washington, 1922, p. 77; 



Publ. 342, 1924, p. 71. 



Test in front view, broadly elliptical; in end view, compressed; 

 chambers biconvex; the periphery with a definitely developed carina; 

 wall smooth, except for occasional transverse ribs usually indistinct; 

 aperture slightly produced, broadly elhptical, with a slightly thick- 

 ened border joining the carina at its outer edge; the aperture with a 

 small bifid tooth. 



The record for this species in the West Indian region rests on a 

 single specimen from the Tortugas material. The specimen is here 



