552 MOLLUSCA. 
3. Spherium martensi. (Tab. XLII. figg. 3, 3a, 6.) 
Spherium martensi, Pilsbry, Proc. Acad. Phil. 1899, p. 401°. 
Rather large and fragile, in general outline like the preceding, but with broader summits and much thinner 
teeth. Summits somewhat swollen, but not distinctly circumscribed as in the subgenus Calyculina. 
Long. 154, alt. 11, diam. 73 millim. 
Hab. Centra, Mexico: Tzintzuntzan, Lake Patzcuaro, State of Michoacan (Mr. & 
Mrs. S. N. Rhoads?). 
4, Spherium luridum, sp.n. (Tab. XLIII. figg. 2, 2 a, 0, ¢.) 
Transversely oval, distinctly unequilateral, solid, moderately convex ; beaks full, obtuse, scarcely raised above 
the outline of the shell, decorticated; anterior part broadly rounded, posterior lower and subangular ; 
ventral margin very slightly arcuated in the middle part, more ascending before than behind; outside 
with regular close-set concentric ridges, dull yellowish-brown, not shining ; hinge-margin thin, cardinal 
teeth feeble, anterior lateral tooth rather strong, but short, distinctly curved, posterior lateral tooth thinner 
and longer ; inside white or pale grey. 
Long. 9-10, alt. 7, diam. 44-5 millim. Vertices in 2 long. 
Hab. N.W. Mexico: Ameca, State of Jalisco (Richardson). 
Near S. sulcatum, Lam. (simile, Say), and S. awreum, Prime, from North America, 
but of smaller size and with more curved hinge-margin than the former, comparatively 
more oblong, with the summits not so prominent and the ventral margin less arcuated 
than the latter, besides being somewhat more unequilateral than both. 
Younger specimens are also a little more equilateral and more orbicular than the 
full-grown ones, viz.:—Long. 64, alt. 5, diam. 3$ millim.; vertices in # long. 
The very young examples which are found within the shell of the parent animal 
measure 2°6 millim. in length, 2:1 in height, and 0°6 in diameter (see fig. 2 ¢). 
5. Spherium costaricanum, sp.n. (Tab. XLIII. figg. 1, 1a, d.) 
Testa parva, subeequilatera, modice convexa, striis concentricis tenuibus sculpta, pallide grisea, zona marginali 
flava, antice breviter rotundata, postice subrostrata, margine dorsali antrorsum et retrorsum declivi, marg. 
ventrali sat arcuato; verticibus vix prominulis, rubescentibus. 
a. Long. 4:8, alt. 4:0, diam. 2°5 millim. Vertices in 3 long. 
b. 99 4:5, 99 3°5, 99 2°3 29 99 + 99 
é. 29 4-1, 29 3°), 99 1:7 99 99 q 99 
d. 55 40, ,, 33, ,, 2°0 ” ” 3 ” 
é. ” 31, 5, 2°6, ” 1:45 ” ” 3 ” 
a. Specimen from Alajuela; 6-e. Specimens from La Palma. 
Hab. Centrau Costa Rica: La Palma, alt. 1500-1600 metres, in swamps (Biolley & 
Pittier); Alajuela, alt. 900-1000 metres (Orosco). 
EUPERA. 
Eupera, Bourguignat, Amenités Malac. i. pp. 80, 61 (1854). 
Limosina, Clessin, Malak. Blatt. xix. p. 160 (1871). 
Shell of smail size, the part before the summits shorter and lower than that behind 
them; in each valve one cardinal tooth only; anterior and posterior lateral tooth 
