86 



BULLETIN 71, UNITED STATES NATIONAL MUSEUM. 



Fig. 42.— Early chambers oi 

 Peneroplis pertusus, var 

 arietinus, X100. Micro 



SPHERIC PROLOCULUM 18/i IT 

 DIAMETER. 



All of the earlier chambers of Peneroplis have similar apertures 

 but in later coils there are developed multiple apertures in some 



cases. Certain forms may complete their 

 tests with all of the apertures single; others 

 may have multiple apertures developed fairly 

 early. This apparently has a defini te relation 

 to the form of the test. 



The microspheric form of the test (fig. 42) 

 differs from the megalospheric form in the 

 size of the proloculum, the number of coils in 

 the test, and especially in the loss of the 

 Gornuspira-hke second chamber. The same 

 condition will be noted in the two following 

 genera, Orbiculina and Orbitolites. This is a 

 very peculiar condition in which the micro- 

 spheric form is the more accelerated in this 

 respect, while in most of the genera of the 

 family it is the megalospheric form which is 

 the most accelerated and therefore most apt to skip certain of the 

 early stages. 



PENEROPLIS PERTUSUS (Forskll). 



Plate 36, fig. 1; plate 37, figs. 1, 2, 6. 



Nautilus pertusus ForskIl, Descr. Anim., 1775, p. 125, No. 65. 

 Peneroplis pertusus Jones, Parker, and H. B. Brady, Foram. Crag., 1865, p. 

 19— H. B. Brady, Rep. Voy. Challenger, 1884, p. 204, pi. 13, figs. 16, 17. 



Description. — Test planospiral, composed of several coils, central 

 umbilical portion usually visible throughout the development of the 

 test, chambers numerous, increasing gradually in height, but the test 

 close coiled throughout; sutures somewhat depressed, wall marked 

 by longitudinal, slightly oblique lines; aperture consisting of numer- 

 ous slightly elongate pores along the apertural face, the whole with a 

 thickened Up. 



Diameter, up to 2 mm. 



Distribution. — Bagg records this typical form from Albatross station 

 4017 in 305 fathoms near the Hawaiian Islands and Rhumbler from 

 shore sands of Laysan Island. In the Nero material the typical form 

 has occurred at numerous stations off the Hawaiian Islands in from 

 22 to 271 fathoms, off Guam, Nero 1466 in 234 fathoms, from Manila 

 Bay and from Gaspar Straits, North Pacific Exploring Expedition, 

 Captain Rodgers. It also occurred at Tuscarora 60, latitude 21° 14' 

 N.; longitude 157° 36' W. in 63 fathoms. 



Besides this typical, planospiral, closely coiled form, there are 

 several different forms which seem worthy of at least varietal dis- 

 tinction. In the material at my disposal these do not seem to have 



