340 PROCEEDINGS OF THE ACADEMY OF [PaRT II 



Length 61.3, diam. 13.6 mm. The largest one is somewhat 

 broken, but evidently had a length of about 75 mm. 

 Type and 12 other specimens are no. 3263 A. N. S. P. 



Mitra titan Gabb. Plate XXIV, flgs 1, 2. 



Mitm. titan Gabb, Trans. Amer. Phil. Soc. xv. 1873, p. 220. 

 Mitra symmetrica Gabb, I. c. 



This large species reminds one of M. inUlingtoni Conr., from the 

 Jacksonian Eocene, but has finer revolving and more prominent 

 longitudinal lines, it is also somewhat wider in proportion to its 

 length. 



The adult stage is represented by one specimen, broken at both 

 ends (PL XXIV, fig. 2), in its mutilated condition measuring, length 

 106.3, diam 43 mm. The spire shows fine spirals, every fourth one 

 deeper; tapering base densely striate spirally, the peripheral region 

 of the last whorl being smooth. In the young stage, represented 

 by Gabb's Mitra symmetrica (PI. XXIV, fig. 1), the whole surface is 

 closely sculptured with spiral cords, on the upper part of the last 

 whorl alternating with smaller threads; the intervals being beauti- 

 fully sculptured with very fine axial threads as in M. longa. Length 

 of M. symmetrica 51.2, diam. 13.8 mm. The types of both M. titan 

 and M. symmetrica show four columellar plaits, the lower one small 

 and hardly visible in a front view. 



Five specimens around 50 to 80 mm. long, afford the stages con- 

 necting symmetrica and titan. 



Type of M. titan no. 3261 A. N. S. P. 5 smaller specimens are 

 contained in no. 3267. 



Type of M. stjmmetrica no. 3260 A. N. S. P. 



Mitra rudis Gabb. Plate XXIV, flgs. 4, 5. 



Mitra rudis Gabb, Tr. Am. Philos. Soc. xv, 1873, p. 220. 

 Mitra quemadica Maury, Bull. Amer. Pal. v, p. 75. 



The last whorl has about nineteen low, rounded, spiral cords, 

 five of which are visible on the whorls of the spire. These are 

 crossed and made subgranular by very irregular, subobsolete, axial 

 wrinkles or growth lines. In the adolescent shell there are raised 

 threads across the intervals, which appear pitted. Between the 

 upper spiral cord and the next, there is a wider interval. 



Length (summit broken) 31.3, diam. 13.8 mm. 



Type is no. 3262 A. N. S. P., with 5 smaller examples. 



Mitra granulosa Lamarck. 



We refer a young specimen 18 mm. long to this recent species. 



