INSTITUTE OF SCIENCE, PHILADELPHIA. 325 



beside the nucleus ; umbilicus shaped like that of /^a/w/^r-rw with no rib but, 

 as well as the rest of the surface, finely regularly spirally threaded, the threads 

 delicately reticulated by arcuate lines of growth ; form depressed, the umbili- 

 cal carina simple, the upper surface of the whorls somewhat rounded, but bor- 

 dered by a double, elevated thread, while the periphery (including the lateral 

 aspect of this thread) has a vertical surface, like the tire of a wheel, which 

 offers three strong, elevated, rounded threads with two fine intercalary elevated 

 lines. Alt. of shell 2.0; max. diam. 5.3 mm. 



This interesting form is of course young, and may develop an umbilical 

 rib, or may, when adult, have a decumbent keel, in which case it would be 

 referable to Patidaxis. In its present state it differs from all the species of 

 that section in its sculpture and its ribbed periphery, and from the young of 

 all the species of Solariaxis by the absence of any well-defined umbilical rib. 

 It may turn out to represent a distinct section. 



S. periscelidmn n. s. (pi. 22, fig. 11). Shell depressed, rather small, with 

 four or more post-nuclear whorls ; periphery with a rather strong annulate 

 rib with a fainter one on each side, the one behind separated by a well-marked, 

 sometimes excavated, interspace ; suture appressed, with a granular line in 

 front of it and often several feebler rows in front of that, the surface of this 

 part of the whorl somewhat concave or flattish ; base rounded from the keel 

 to the umbilical carina, which is nodular, with or without a few broken fine 

 spirals outside of it, crossed by weakening radial wrinkles ; umbilicus rather 

 wide, with a small, well-marked, annulate umbilical rib, and the walls trans- 

 versely wrinkled and somewhat concave. Alt. 4.2 ; max. diam. 9.0 mm. 



This interesting species is from Mr. Aldrich's collection, where I find 

 three specimens from Matthews' Landing, on the Alabama River. Its nearest 

 relative is 6'. Aldriclii, which has much coarser and somewhat different sculpt- 

 ure and a narrower umbilicus. The present species is destitute of the flat 

 basal spirals of S. Aldriclii. 



5. ^/c/n'c/z? n. s. (pi. 22, figs. 13, 13 a) is another species of the same group, 

 with beautifully compact and clear-cut sculpture. The umbilical rib and carina 

 are equal and similar, the wall between them excavated ; the carina has twenty- 

 four strong annular tubercles, outside of which are three broad flat and 

 three or four thread-like spirals, all, as well as the interspaces and umbilical 

 wall, regularly wrinkled ; outside of these is a more prominent thread, then a 

 small one, then the broad, blunt peripheral carina ; above there are two 

 strong beaded threads, separated by a fine one behind, and in front of the 

 suture a more or less conspicuous spiral, with three smaller ones in front of 

 the latter. The shell is moderately depressed, and all the sculpture is regular 

 and not sharply elevated. Alt. 5.5; diam. lO.J mm. From Lisbon, Ala., 

 and the Wahtubbee Hills. 



S. Leaiium n. s. (pi. 22, fig. 12) is from the Wahtubbee Eocene, and one of 

 the most attractive forms of the group. The umbilical carina is annulate with 



