GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 95 



The vertical section shows very peculiar embryonic chambers in 

 that they do not exhibit the usual characters of American species, but 

 have a broad and much flattened central chamber two to four times 

 as broad as high with a compressed, partially encircling chamber, 

 which in section is usually cut on the opposite sides of the central 

 chamber. In some cases there seems to be an irregular mass of three 

 or four more or less nearly spherical chambers. In the former case 

 these central chambers in section are nearly as wide as the whole 

 umbonal portion of the test. Lateral chambers, usually about twice 

 as wide as high, the outer wall often somewhat arched toward the 

 exterior of the test, arranged in vertical columns. Pillars not dis- 

 tinct except in the central portion where there are a few strong ones 

 increasing rather rapidly in diameter toward the periphery, usually 

 about 9 or 10 chambers in a vertical column in the center of the 

 umbilical region. The peripheral region has only a thin coating of 

 lateral chambers, the last formed layer present only on the outer 

 half of the periphery and often none at all present on the last quar- 

 ter of the test toward the periphery, the surface being made up by 

 upper and lower walls of the equatorial chambers. Equatorial cham- 

 bers numerous, comparatively broad, the peripheral wall convex out- 

 wardly tow ard the peripheiy, the chambers at least as wide as high. 



In horizontal section the equatorial chambers are usually some- 

 what irregularly hexagonal near the center, toward the periphery 

 more or less rhomboid with the outer peripheral wall curved. 



As far as described material is concerned this is an unusual form 

 for American species of Lepidocydina, especially in its embryonic 

 chambers. 



Occurrence. — Type-specimen, vertical sections, U. S. National 

 Museum Catalogue No. 324741. The species is fairly abundant at 

 stations 6586e and 6587 from near the mouth of Tonosi River, 

 Panama, D. F. MacDonald, collector. It was also collected by Mac- 

 Donald at station 6512, river bed, David. 



At stations 6010, 600 or 700 feet south of the Miraflores Locks, and 

 6012a and 6012c, south of Empire Bridge, in the Culebra formation, 

 specimens of small orbitoids occur, but they are not sufficiently well 

 preserved for positive identification. Although those from the latter 

 station seem somewhat like L. panamanensis in their thin borders 

 and raised center with papillae, they can not be specifically identified 

 with certainty. At other stations poorly preserved orbitoid fo- 

 raminifera occur, but their specific identity can not be accurately 

 determined. Specimens doubtfully referable to L. panamensis were 

 obtained in the Emperador limestone, at station 6015, Empire. 



