10 PROCEEDINGS OF THE NATIONAL. MUSEUM vol.76 



The first eight annuli are rather narrow, 30/x to 40ju wide, beyond 

 which the width is between SO/x and lOO/x. The chambers are rectan- 

 gular; the radial diameter the same as the width of the annuli; 

 tangential diameters between 40/i and 65/:. The earlier chambers 

 are square; the later ones are elongate. The radial wails of chambers 

 in adjacent annuU may or may not be in alignment. The height of 

 the chamber cavities at the center is about 10/u; at the periphery, 

 1 mm.; from the center, about SS/t. The roofs and floors are rather 

 thin, ranging from 4jLt to 12/i thick, and are finely perforate; the 

 perforations are about l/j. across. Chambers in the same annulus 

 communicate by stolons at the distal ends of the chambers, not at the 

 proximal ends as in Discocydina pratti; chambers of adjacent annuli 

 connected by stolons that pass through the annular walls. 



Lateral chambers well developed, four or five layers over the center. 

 There is a free edge equal to the width of one annulus, about 120ju 

 in the specimen here described. Height of cavities variable, range 

 from a barely detectable slit to I5ii. Length also variable, range 

 from 8/1 to SO/t. Roofs range from 7/i to 15m thick, about the same 

 as the height of the chamber cavities. There are no definite vertical 

 tiers of lateral chambers. Small pillars present, as much as 25/i in 

 diameter at the surface; some appear to have their origin at the 

 equatorial layer. 



Localities and geologic horizon. — All localities in State of Vera Cruz. 

 Soledad Crossing over Rio La Puerta, Canton Tuxpan, collected by 

 T. W. Vaughan (M. 84 V.); Rio Tuxpan, mouth of Rio Pantepec, 

 collected by Paul Weaver (M. 65 V.) ; Zardo Creek, Canton Tan- 

 toyuca, 0.7 km. southwest of Tierra Colorada, collected by T. W. 

 Vaughan (M. 115 V.); Guayabal, collected by W. S. Cole. Guaya- 

 bal formation, upper middle Eocene. 



Cotypes.—Csii. No. 352881, U.S.N.M. 



Since the specimens belonging to this species are extraordinarily 

 well preserved, an endeavor was made to make an especially thorough 

 study of its minute structure. Accordingly a section was impreg- 

 nated with balsam and decalcified according to the method described 

 by Hofker,* and it was compared with a similarly prepared section 

 of Eeterostegina suborbicularis d'Orbigny from Tonga Islands. The 

 preparation of the last species shows the canal system filled with 

 balsam while the calcareous test had been removed. Therefore, it 

 served as an excellent basis for the study of the preparation of 

 Discocydina perpusilla. 



The stoloniferous passages between the equatorial chambers of the 

 same annulus, the passages between successive annuli, and the per- 

 forations of chamber roofs and floors were perfectly shown in D. 

 perpusilla, but there was no trace of any canals in either the annular 



<Hofker, The foraminifera of the Siboga Expedition, Pt. 1, 1927, p. 2. 



