358 BULLETIN iOO, UNITED STATES NATIONAL MUSEUM. 



SIDEROHTES TKTKAEDEA (GUmbel). 



Plate 75, fig. 5; plate 76, figs. 1-5. 



Calcarina tclracdra Gumbel, Abh. bay. Akad. Wiss., vol. 10, 1868 (1870), p. 656, 



pi. 2, figs. 97fl., b. 

 Siderolites tetraedra Cushman, Bull. 100, U. S. Nat. Mus., vol. 1, pt. 6, 1919, pi. 



44, fig. 5; pi. 45, figa. 1-5. 



Description. — Tost in the young, biconvex, rotaliform, composed 

 of two or more volutions, with several chambers in each; later the 

 supplementary skeleton greatly developed and the exterior with 

 irregularly placed chambers, subglobular in shape and with coarsely 

 perforated walls; between the chambers, solid radial portions giving 

 support to the remainder of the test, and at four or five (usually four) 

 points thick tapering, bluntly pointed spinose projections are placed, 

 having then* initiation in the early portion of the test, in the adult 

 these often covered nearl}' to the tips with the supplementary skele- 

 ton, in such cases the whole test instead of spherical being concave 

 and polyhedral; aperture in the young at the base of the chamber, 

 in the adult formed by the large perforations of the chamber wall. 



Diameter up to 6 mm. 



In the Philippine collections this species is often very abundant 

 in all its stages. It is most common in warm, shallow water. It 

 has occurred at the following localities: Jolo Jolo; off Romblon; 

 between Burias and Luzon; China Sea, off southern Luzon; Malam- 

 paya Sound; Palawan Island; north of Tawi Tawi; and Darvel 

 Bay, Borneo. 



There seems to be little to separate this species from that described 

 from the Eocene by Giimbel. The four tapering spines are very 

 characteristic. Various stages in the development of the species 

 are shown on plate 76, from the early Calcarina stage through the 

 development of a few of the irregular chambers and gradually the 

 covering of the surface with these. An eroded specimen is shown in 

 figure 4, where the chambers of the exterior have been partially 

 broken away leaving the heavier solid supporting portions as pro- 

 jections. 



Carpenter figures this species as a "Philippine variety" of Tino- 

 porus haculatus,^^ and makes notes of its differences from the "Aus- 

 tralian variety" (Baculogypsina sphaerulatus) . He showed the 

 differences in the structure of the interior also. 



From what I have seen of this species it is very common in the 

 Philippines, but rare elsewhere, while the following genus and species 

 is rare in the Philippines but very abundant in the southern region 

 about Austra,lia especially. 



In its development Siderolites stands between Calcarina and Baculo- 

 gypsina, and geologically also its first occurrence is between the two 

 as far as is known. 



«• Introd. Foram., 1862, pi. 15, figs. 8-10. 



