POLYMESODA.—RAPANA. 593 
17. Polymesoda salmacida*. 
Cyrena salmacida, Morelet, Test. Noviss. ii. p- 26 (1851) *; Deshayes, Catal. Conch. Brit. Mus. 11. 
p- 259°; Prime, Ann. Lyc. Nat. Hist. N. York, vii. p. 315, t. 1. figg. 1, la,d (1862) °; 
Monogr. Am. Corbiculade, p. 29, fig. 22*; Sowerby, in Reeve’s Conch. Icon. xx. t. 17. 
fig. 106°; Fisch. & Crosse, Miss. Scient. Mex., Moll. ii. p. 642, t. 61. figg. 6, 6a, 7°. 
Ovate, more or less beaked behind, pale reddish with concentric darker bands, without distinct periostracum. 
a. Long. 27, alt. 19, diam. ? millim. Vertices in ? long. 
b. ” 25, ” 19, ” 13 ” 
C. 9 27, ” 18, ” 12 ” ” 3” 
a. Morelet’s measurements; 4. Fischer and Crosse’s fig. 6; c. Fischer and Crosse’s fig. 7. 
Hab. Yucatan: Sisal, in marshes near the sea (paludibus maritimis) (Morelet 145°), 
As Morelet found dead shells only (“ testas inanes”) it is not quite certain that the 
living shell is entirely without periostracum, or that it lives in brackish water; the 
other species of this subdivision of Polymesoda, however, live in places reached by the 
tide. Fischer and Crosse § treat the more distinctly beaked form (their figure 7) as a 
variety, swbrostrata, but it seems to me to be nothing more than an individual variation ; 
moreover, Morelet’s description (‘‘ subrostrata”) and measurements agree better with 
their fig. 7 than with fig. 6. 
” 2 ” 
1 
3 
Besides the shells belonging to genera either strictly submarine or common to fresh 
and brackish water, there live at the mouths of the rivers or in the mangrove-swamps 
of Central America several species of truly marine genera. Though they do not actually 
come within the scope of this work, it is advisable to briefly notice such as have been 
recorded from the coasts of the region under investigation. 
GASTROPODA RHACHIGLOSSA. 
Rapana kiosquiformis. 
Purpura kiosquiformis, Duclos, Ann. Sci. Nat. (1) xxvi. p. 107, t. 1. fig. 5 (1832) *; Kiener, Icono- 
graphie, Purpura, p. 59, t. 15. fig. 40°; Deshayes, in Lamarck’s Hist. Nat. des Anim. sans 
Vert. ed. 2, x. p. 96°; Eydoux et Souleyet, Voyage de la Bonite, Zool. ii. p. 608, t. 59. 
figg. 23-25 (with living animal and operculum) * (copied in M, A. Gray’s Fig. Moll. Anim. 
ii. t. 87 a. fig. 6, and in H. & A. Adams, Gen. Recent Moll. t. 14. fig. 3) ; Reeve, Conch. 
Icon. iii. t. 7. fig. 31°; C. B. Adams, Ann. Lyc. Nat. Hist. N. York, v. p. 301 (1854) °. 
Cuma kiosquiformis, H. & A. Adams, Gen. Recent Moll. i. pp. 133, 1347; Troschel, Gebiss d. 
Schnecken, ii. p. 137, t. 13. fig. 11 (radula) °. 
Purpura scalariformis (Lam.), d’Orbigny, Voy. Am. mér., Moll. p. 487 4 
Shell somewhat biconic, with a strong, sharply knobbed, tuberculated middle keel and some more feeble spiral 
ridges below it; suture deep, in the last whorls peculiarly festooned ; aperture oblong-oval, outer margin 
rather curved, crenulated ; columellar margin dilated, appressed ; channel short, bent backwards, forming 
a strong spiral ridge round the undermost part of the shell. Mud-coloured, aperture white or pale yellow. 
Long. 42-61, diam. 27-88; apert. 26-35 millim. 
* * Salmacida aqua,” in Pliny, “ water a little salted.” 
BIOL. CENTR.-AMER., Terr. and Fluviat. Mollusca, Movember 1900. 95 
