PACHYCHILUS. 457 
Near P. indiorum, but differing from it in having a remarkable sinus in the upper part of the external 
margin of the aperture and a shallower one below, the middle part in consequence projecting as in the 
genus Melanatria. This sinuosity appears only in adult shells, the strie of growth half a whorl 
backward of the aperture being quite straight. As five aduit specimens are known, we may presume 
that it is not a monstrosity. 
Hab. S.W. Muxico: Tehuantepec (Dr. Spear 12). 
I give a copy of Pilsbry’s figure. 
12. Pachychilus chrysalis. (Tab. XXVII. figg. 6-9, juv.; 15-18.) 
Melania chrysalis, Brot, Matériaux fam. Mélaniens, iii. p. 39, t. 2. fig. 5 (1872) *; in Martini & 
Chemnitz, Syst. Conch.-Cab. ed. 2, Melaniaceen, p. 47, t. 5. fig. 11”. 
Pachychilus chrysalis, Fisch. & Crosse, Miss. Scient. Mex., Moll. ii. p. 342, t. 51. figg. 8, 8a-c’*; 
Pilsbry, Proc. Acad. Phil. 1892, p. 340%. 
Pachychilus chrysalis, var. 8. vulnerata, Fisch. & Crosse, loc. cit. p. 342, t. 51. figg. 9, 9a, 10, 10a’. 
Pachychilus larvatus, Brot, Syst. Conch.-Cab. ed. 2, Melaniaceen, p. 336, t. 34. figg. 11, ll a—e°; 
Fisch. & Crosse, loc. cit. p. 344’. 
Last; whorl comparatively long and compressed, giving this species the appearance of a pupa (or chrysalis) of 
a large moth. 
Hab. S.E. Mexico: San Pedro Gineta, on the Isthmus of Tehuantepec, State of 
Chiapas (Suwmichrast 5°"); Ixtacomitan, Chiapas (Rovirosa*); Teapa, Tabasco 
(H. H. Smith). | 
The habitat of the typical specimens is given as ‘“ Tehuantepec” (Geale}?): I 
presume that this refers also to the shells collected there by Sumichrast. 
The examination of a considerable number of specimens collected by Mr. H. H. 
Smith at Teapa shows that Brot’s var. /arvatus and Fischer and Crosse’s var. vudneratus 
cannot be maintained as distinct varieties; they are only individual differences caused 
by more or less extended erosion of the upper whorls. The dimensions of a few 
selected specimens from Teapa are as follows :— 
. Long. 52, diam. 24; apert. long. 24, diam. 17 millim. Anfr. superst. 33. 
a 
b ys On oy 4S 9 23, » 163 ., ” 3. 
¢ » 90, 5 22 ; 9 23, ,, 14 ” ” 4. 
eo a 5 80: oo 0, ay HA, oA 
é. wo O2y, wm 13 9 15, ,, 10 ” ” 53. 
f wy 20, (1S; ” 123, ” 8&3 ” ” 43. 
g w 18, 11; ” 9, 6 4» ” ? 
q The specimen 0 is nearly as old and full-grown as a, but it is eroded to a greater extent, and therefore distinctly 
shorter than c and d, which are inferior to it in the other dimensions. The specimens e¢, f, and g are evidently 
young, not full-grown, with thin peristome; they are a little more conical, their last whorl being compa- 
ratively broader. 
Var. nympha,n. (Tab. XXVII. figg. 12-14.) 
Of smaller size and comparatively a little narrower. 
Long. 36, diam. 16; apert. long. 15, diam. 10 millim. Anfr. superst. 6. 
” 34, ” 17; ” 162, wo AL ” ” 42. 
BIOL. CENTR.-AMER., Terr. and Fluviat. Mollusca, November 1899. 58 
