FAMILY 26. PENEROPLIDAE 223 



Genus OPERTORBITOLITES Nuttall, 1925 



Plate 32, figure 7 

 Genoholotype, Opertorbitolites douvillei Nuttall 

 Opertorhitolites NuTTALL, Quart. Journ. Geol. Soc, vol. 81, 1925, p. 447. 



Test circular, lenticular, consisting of a median chamber- 

 layer resembling that of Orbitolites with a thick imperforate 

 lamina of shelly material on each side of the median layer. 



Eocene. India. 



Genus CRATERITES Heron-Allen and Earland, 1924 



Plate 32, figure 20 



Genoholotype, Craterifes rectus Heron-Allen and Earland 

 Craterites Heron-Allen and Earland, Journ. Linn. Soc. Zool., vol. 35, 

 1924, p. 611. 



Test probably attached in life, the whole composed of nu- 

 merous layers of chambers, the basal layer without trace of 

 spiral development, form in side view contracted above the base, 

 and the outer end broadening and convex; chambers very 

 numerous; wall calcareous; outer surface with numerous small 

 rounded openings. 



The type specimen is the only one known. It is from shallow 

 water off Lord Howe Island, South Pacific. Through the 

 courtesy of the authors, I was enabled to study the holotype 

 now in the Heron-Allen and Earland Collection in the British 

 Museum. It is very difficult to understand the full relation- 

 ships of this peculiar form until more specimens are found. 

 In some respects it resembles Gypsina and its allies, but it is here 

 left where the authors placed it, near Orbitolites. 



The Peneroplidae present a fairly regular series from simple 

 to complex in their structure. In the present oceans they are 

 limited to shallow warm waters, a habitat they seem to have 

 preferred through their geologic history. The early perforate 

 chambers form a very puzzling problem in the classification of 

 the group showing that they were derived from a perforate 

 ancestry. Just what that ancestry may be is not easily seen 

 at present but must be solved by a study of Cretaceous material 

 where there are forms referred to Peyieroplis that seem to hold 

 the clue to this problem. They have kept to the planispiral form 

 and in many ways show a close resemblance to the Camerinidae. 



