412 CRETACEOUS PALEONTOLOGY. 



the hinge-line in an obtuse angle. On the internal casts the free 

 margins of the shell are more or less keeled, and the muscular 

 impressions are of moderate size and rather clearly marked. 

 Surface of the casts marked by rather coarse ribs which become 

 more and more obsolete as they approach the umbo. 



Remarks. — This species rarely preserves any portion of the 

 shell substance, usually being in the form of internal casts. 

 Several similar forms have apparently been described as distinct, 

 which should in all probability be included in one species, a de- 

 cision arrived at after a careful study of the types of all the forms. 

 The first name applied to any of the forms was Area quindecem- 

 radiata, and fortunately, too, the original specimen to which this 

 name was applied represents the most typical form of the species. 

 The type of Cibota multjradiata Gabb, is apparently a young in- 

 dividual, with no characters by which it can be separated specifi- 

 cally from A. quindecemradiata; the horizon and locality given 

 for this specimen is "Green marl, MuUica Hill, N. J.," but the 

 lithologic character of the specimen would indicate that it was 

 not collected from the Navesink horizon at that locality, but from 

 one of the higher beds. The type specimen of Area altirostris 

 Gabb, is labeled "Crosswicks N. J.," which is rather indefinite 

 since specimens which are apparently from various horizons and 

 localities along Crosswicks Creek are soi labeled in the old collec- 

 tions, an entire section of the Cretaceous strata being exposed 

 along this stream. The specimen is a small internal cast and the 

 absence of the radiating ribs which are present upon the typical 

 Area qmndeeemradiata, is doubtless due to the youth of the 

 specimen and its condition of preservation. The type specimen 

 of Cucullaea transversa Gabb is said to be "probably from Arney- 

 town, N. J.," which would indicate the Navesink horizon, but 

 the exact locality is left in doubt. Whitfield was mistaken in his 

 identification of the type of this species, but since the publication 

 of his monograph, the type has been found in the collection of 

 the Philadelphia Academy of Science, and an examination of it 

 shows it to be nothing more than an exceptionally large individual 

 of Area quindeeemradiata. In 1905 Johnson proposed to sub- 

 stitute the name Cueullaea gabbi for C. transversa Gabb, because 

 of the prior use of that name by Rogers in 1839. 



