ORTHAULAX, A TERTIARY GUIDE FOSSIL. 



25 



In the United States OrfhaiiJax hiornatns has 

 never been found in l)eds as young as the 

 Chipola marl (lower Miocene), but it occurs in 

 the ''silex bed" of the next oldei' formation, 

 the Tampa, which is regarded as of upper Ohgo- 

 cene age. The species has also been listed by 

 Dall " from the Chattahoochee formation on 

 Flint River, Ga., but the specunen so named 

 in the collection of the United States Na- 

 tional Museum (an impression of a fragment, 

 U. S. Nat. Mus. catalogue No. 166787) appears 

 to be 0. pugnax. 



The two large specimens of Orthaiilax from 

 Cuba which I figured as 0. iimrnatus ' proved, 

 on cutting, to be different, and they are here 

 described under the name Oiihaulax caepa. 



O/ihaulax gabht. — The stratigraphic range of 

 Orthaulax gabbl Dall appears to be very nearly 

 the same as that of 0. inornatus, but the two 

 species have not yet been found in the same 

 beds. Orthaulax gabbl has not hitherto been 

 reported outside of Florida, where it is abun- 

 dant in the Chipola marl member of the Alum 

 Bluff formation, but it occurs also in the upper 

 part of the Culebra formation and in the 

 Emperador limestone at several places in the 

 Canal Zone. Some of the Panaman specimens 

 simulate very closely the external form of 

 Orthaiilax pugnax, and it is only in cross section 

 that their true relationships become evident. 



The known range of Orthaulax gabbi is upper 

 Oligocene and lower Miocene. 



Orthaulax pugnax. — The type of Orthaulax 

 pugnax (Heilprin) comes fi-om the "silex bed" 

 of the Tampa formation. The species is com- 

 mon in the lower part of the Chattahoochee for- 

 mation on Flint River, Ga., and ithas beenfouud 

 also in beds of the same age in Alabama and 

 Ajitigua. My identifications of specimens of 

 Orthaulax pugnax from Anguilla " and from 

 Panama," which were based upon external 

 form alone, are wrong; axial sections show the 



»U. S. Nat. Mus. Proc, vol. 51, p. 509, 1910. Plate 88, figure 9, rep- 

 resents a specimen from Ballast Point, Fla., U. S. Nat. Mus. catalogue 

 No. 163099. 



^ Cooke, c . ^V . , Tertiary mollusks from the Leeward Islands aui 1 ' ii I )a : 

 Carnegie Inst. Washington Pub. 291, p. 116, pi. 2, figs. 1, 2, 1919. 



« Carnegie Inst. Washington Pub. 291, p. 115, pi. 2, fig. 3, 1919. 



9 U. S. Nat. Mus. Hull. 103, p. 550, 1919. 



first probably to be refera])lc to O. agiiadillensis 

 and the second to O. gahhi. 



The stratigraphic range of O. pugnax is there- 

 fore middle and uppei' Oligocene. 



Ortha ulax aguadillcnsic. — Ortha ulax aguadil- 

 lensis Maury is widely distributed in the West 

 Indies but has not yet been reported from the 

 continents. The type was taken by Reeds 

 from the Aguadilla limestone at Aguadilla, 

 P. R. It is probable that some of the sp(>ci- 

 mens of Ortliaulax collected by Hubbard '" 

 elsewhere in Porto Rico belong to this species. 

 Large casts of Orthaulax that appear to be refer- 

 al)le to (>. aguadillensis have been found on St. 

 Croix (see PL III, hg. 4), and one poorly pre- 

 served specimen which seems to be 0. aguadil- 

 lensis comes from the upper Oligocene Anguilla 

 limestone of Anguilla. In Santo Domingo this 

 species has Ijeen collected at widely separated 

 localities; it is fairly abundant but poorly pre- 

 served in the Cevicos limestone (upper Oligo- 

 cene) near the east end of the Cibao Valley, 

 and excellent specimens have been obtained 

 from beds supposed to be of Miocene age at 

 two localities in the valley of Rio Yaque del 

 Sur. 



The stratigraphic range of Orthaulax aguadil- 

 lensis appears to be upper Oligocene and 

 Miocene. 



Orthaulax caepa. — Orthaulax caepa Cooke, 

 n. sp., is known from only one locality, Consola- 

 cion del Sur, Pinar del Rio, Cuba. Specimens 

 of this species, which I at first mistook for 

 Orthaulax inornatus, proved, when cut, to be 

 more closely related to 0. aguadillensis but to 

 be different from both. The age of the lime- 

 stone at Consolacion del Sur is not known, but 

 it is thought to be upper Oligocene. 



Correlation table. — In order that the strati- 

 graphic positions occupied by the species of 

 Orthaulax may be more readily visualized, the 

 accompanying correlation table has been pre- 

 pared. The table is not complete but shows 

 only those formations in which Orthaulax has 

 been found and enough others to give a strati- 

 graphic ])ackground. 



I'' Uubbard, Bela, Science, new ser., vol. 51, p. 396, 1920. 



