304 REPORT OF NATIONAL MUSEUM, 1897. 



PENEROPLIS PERTUSUS Forskal. 

 (Plate 48, fig. 4.) 



This species includes a wide variety of forms presenting all the inter- 

 mediate stages from thick, slightly compressed, nautiloid shells, to the 

 long, cylindrical, crosier- shaped "varieties, and from these to the thin, 

 compressed, rapidly widening forms. In all varieties the chambers 

 are without divisions or constrictions, the apertures are porous, and 

 the surface, with few exceptions, is striate. 



Localities. — Straits of Yucatan and Exuma Sounds (stations 2352, 

 2629), 463 and 1,169 fathoms. 



PENEROPLIS PERTUSUS, variety DISCOIDEUS, new. 



(Plate 49, fig. 1.) 



In this variety the final chambers completely surround the primary 

 convolutions, forming a circular, thin disk resembling the discoidal 

 forms of Orbulina, but distinguished by the entire absence of septa in 

 the individual chambers. 



Locality. — Key West Harbor; shallow water. 



Genus ORBICULINA. 



Chambers subdivided by transverse secondary septa; early segments 

 embracing; arrangement either planoSpiral throughout or partly cycli- 

 cal; contour nautiloid, auricular, crosier- shaped, or complanate. 



ORBICULINA ADUNCA Fichtel and Moll. 

 (Plate 50, fig. 1.) 



The only species of the genus. A planospiral, porcellanous, imper- 

 forate, polished shell, varying in contour from crosier-shaped to dis- 

 coidal; surface usually pitted with minute depressions; the early 

 convolutions embracing; chambers narrow and regularly subdivided; 

 apertures a series of pores in two or more rows on the outer edge of 

 the final chamber. It is distinguished from Peneroplis by the divided 

 chambers, and from Orbitolites by the embracing early convolutions. 



Localities. — Key West and St. Thomas; shallow water. 



Genus ORBITOLITES. 



Test discoidal; cither spiral (non-embracing) at the commencement, 

 or with one or more inllated primordial chambers; subsequently cycli- 

 cal; chambers more or less regularly divided into chamberlets. 



ORBITOLITES MARGINALIS Lamarck. 

 (Plates 50, fig. 2; 51, fig. 1.) 



Avery thin, complanate, discoidal shell; chambers commencing at 

 the center with a small globular " nucleus,'' followed by arched seg 

 ments arranged spirally in one plane, the segments increasing in 



