424 BULLETIN" 103, UNITED STATES NATIONAL MUSEUM. 



I have selected as the genotype the second species, Thysanus ex- 

 centricus, of which I have seen nearly 700 specimens. 



THYSANUS aff. T. EXCENTRICUS Duncan. 



1863. Thysanus excentricus Duncan, Geol. Soc. London Quart. Journ., vol. 19, 

 p. 439, pi. 16, figs. 3a, 3c. 



Apparently the tall variant of T. excentricus is represented by casts 

 in material from Cuba. 



Locality and geologic occurrence. — Cuba, station 3439, in the La 

 Cruz marl, first railroad cutting east of La Cruz, near Santiago, 

 collected by T. W, Vaughan. 



THYSANUS HAYESI, new species. 



Plate 77, figs. 3, 3a, 3&. 



The type is much damaged, but the three views on plate 77, 

 figures 3, 3a, 3h, give an idea of its form. The corallum, which was 

 about 21 mm. long, 12 mm. tall, and 13 mm. in maximum diameter, 

 is relatively wide, and is unilateral. 



The costae are decidedly prominent, 1 mm. or more tall at the mural 

 edge, and are distant, about 2 mm. between the summits of adjacent 

 costae. Their edges are coarsely and kregularly dentate, the denta- 

 tions compressed transversely to the septal planes, and secondarily 

 spinulose. Toward the base of the corallum the costae become less 

 prominent and are obsolete on the base. There are no distinct 

 secondary costae. 



Nearly all of the septa extend to the columella, they are distant 

 and rather thin; intermediate small septa are rare. Margins dentate. 

 Faces with sharp ridges and coarse granulations. 



Columella trabecular and obscurely lamellate. 



Endothecal dissepiments abundant, thin. 



Locality and geologic occurrence. — Cuba, station 3461, Gorge of 

 Yumuri River, Matanzas, lower Miocene, collected by T. W. Vaughan. 



Type.—^o. 324994, U.S.N.M. 



This species, which I am naming for Dr. C. W. Hayes, is most nearly 

 related to TTiysanus corMcula Duncan, but differs in its more distant, 

 more prominent, and coarser costae. 



Family MUSSIDAE Verrill. 



Genus SYZYGOPHYLLIA Reuss. 



1860. SyzygophylUa'REVSs, K. K. Atad. Wiss.Wien, Mat., Natur. CL, Sitzungber, 

 vol. 39, p. 216, pi. 1, figs. 10-12; pi. 2, fig. 10. 



Type-species. — SyzygopJiyllia hrevis Reuss. 



SYZYGOPHYLLIA HAYESI, new species. 



Plate 106, figs. 1, la, 16. 



Corallum compressed-turbinate in form. Greater diameter 75 mm. ; 

 iCsser diameter 59 mm.; height 40 mm. + . The tip of the base and 



