INSTITUTE OF SCIENCE, PHILADELPHIA. 93 



wider interspaces between the ribs crossed by rounded, coarser, equal spirals, 

 whose interspaces are not channelled and never look punctate ; the ribs are 

 also more shouldered than in Holmes's species, so that the suture of M. Holmesii 

 is more marked, Max. Ion. of shell 4.1 ; max. lat. 1.6 mm., in a shell of six 

 whorls. The columella is plicated by three folds, the posterior the largest. 



Caloosahatchie beds, rather numerous. 



This species is somewhat like M. Partscliii Hoernes from the Vienna Basin, 

 but sufficiently distinct. 



Mitra sp. indet. 

 A single specimen too worn to name was found in Caloosahatchie marl. 

 It has about sixteen ribs and in general resembles a slender M. zvandocnsis, but 

 just below the periphery of the whorl is a marked groove, channelled and cutting 

 the ribs as well as the interspaces. On the earlier whorls this channel revolves 

 a short distance behind the suture, which thus appears double. This character 

 will enable the species to be recognized when perfect specimens are found. 

 There are three folds on the columella and the shell is about the size of the 

 next species. 



Mitra Willcoxii n. s. 

 Plate 3, figure 10. 



Shell of about seven whorls, with sculpture of much the same character 

 as that of M. Holmesii; but on the last whorl the transverse sculpture becomes 

 more or less obsolete, differing in different specimens in this respect. On the 

 one figured there would have been twenty-six transverse ribs, but each alter- 

 nate rib is obsolete, while the others are bulbous at the suture and obsolete on 

 most of the periphery. The spiral sculpture is represented by grooves, 

 squarely channelled and broken into square pits by the foundations of the 

 obsolete ribs which interrupt the spirals. There are about ten spirals on the 

 last whorl, and three or four very strong distant cords on the canal ; aperture 

 narrow, columella short, three-plaited; suture distinct, not channelled; nu- 

 cleus smooth, polished, rather large, as in M. zvandoensis and M. Holmesii. 

 Max. Ion. of shell 8.3 ; max. lat. 2.8 ; Ion. of aperture 3.8 mm. 



Caloosahatchie marl, not rare. 



This neat little species is quite variable, but in all the specimens I have 

 seen the ribs in the adult are more or less obsolete. The square pits recall 

 M. wandoensis ; the. general sculpture of the young shell is more like 

 M. Holmesii, which, when adult, is about half the size of this species. 



Mitra (mississippiensis var. ?) silicata Dall. 



Plate 4, figure 11. 



This shell recalls M. mississippiensis as described by Conrad, from which 



it differs by having one more plait on the columella, and by the appressed 



suture. The pseudomorph in this case is imperfect, and probably the shell 



