ART. 1. TERTIARY MOLLUSKS FROM THE WEST INDIES WOODRING. 7 



outline of specimens of O. aguadillensis from the Dominican Re- 

 public and of O. cae'pa from Cuba, he suggested that the difference 

 may be a sexual feature, although a similar sexual difference is not 

 known in the living species of Strombus. The spiral threads are 

 most conspicuous on medium-sized shells. (See pi. 2, fig. 6.) They 

 are as prominent as on O. caepa^ but are more closely spaced. The 

 layers of shell and callus covering the spire have undulating growth 

 lines similar to those shown in an exaggerated fashion on Maury's 

 figure. (See pi. 1, fig. 1.) 



Orthaulax aguadillensis was described by Maury from a single 

 imperfect specimen collected in Porto Rico from the Aguadilla 

 limestone, wnich is considered of upper Oligocene age. It seems 

 to be very common as casts in the overlying Quebradillas limestone, 

 which is of lower Miocene age. Hubbard called these casts O. porto- 

 ricoensis. A Porto Rican cast (pi. 1, fig. 7), collected at the cut 

 just west of Rio Guajataca on the railroad from Quebradillas to 

 Isabella by G. R. Mansfield (U.S.G.S. station 1/146), is introduced 

 for comparison with casts from the Republic of Haiti (pi. 1, figs. 

 1, 6). The cast shown on Plate 1, Figure 6, was collected at a locality 

 where shells were obtained. One specimen from this locality that 

 has Dart of the shell dissolved revealing the cast conclusively shows 

 that these casts from the Republic of Haiti are 0. aguadillensis. 



All the specimens from the Republic of Plaiti were collected 

 from the upper faunal zone of the Thomonde formation, which is 

 the equivalent of the Baitoa formation of the Dominican Republic, 

 and is of lower Miocene age. The Plaitian specimens duplicate those 

 collected on Rio Yaque del Sur, Dominican Republic, from beds of 

 lower Miocene age. 



The following is a list of the localities in the Republic of Haiti, 

 all of which are in the southeastern part of the Central Plain in the 

 Arrondissements of Las Cahobas and Hinche : 



Crest of Tliomonde anticline, left bank of Riviere Thomonde, 

 about 4 kilometers east-southeast of Thomonde, W. P. Woodring and 

 F. G. Evans, jr., collectors, 1921, five specimens, U.S.G.S. station 

 9782. North limb of Thomonde anticline, about 2.5 kilometers east- 

 northeast of Thomonde on trail to Thomassique, W. P. Woodring 

 and F. G. Evans, jr., collectors, 1921, two specimens, U.S.G.S. station 

 9780. North limb of Thomonde anticline, about 2.8 kilometers east- 

 northeast of Thomonde, W. P. Woodring and F. G. Evans, jr., col- 

 lectors, 1921, two specimens, U.S.G.S. station 9781. North limb of 

 Thomonde anticline, about 4 kilometers north-northwest of Tho- 

 monde on trail to Hinche, W. P. Woodring and F. G. Evans, jr., 

 collectors, 1921, one specimen (cast), U.S.G.S. station 9929. South 

 limb of Thomonde anticline, about 1.3 kilometers south-southeast of 



