118 GASTEROPODA. PURPURAD. 
Stirps 3. Apertura ad sinistram in siphonem apertum pro- 
ducta. 
a. Teste siphon brevissimus. Peritrema posticé planiusculum. 
Apertura ad dextram et ad sinistram acu- 
minata. Siphon recurvus .......... 59. PURPURA. 
Apertura ad dextram acuminata, posticé si- 
nuata. Siphon ad sinistram curvatus.. 60. Hima. 
b. Teste siphon mediocris aut longissimus. Peritrema pos- 
tice conforme. 
Siphon mediocris, recurvus, ad apicem. 
Penitremate tectds,. i. 3. eek ee ck 61. BuccinumM. 
Siphon elongatus aut longissimus, rectus, 
ad apicem. Peritremate nullo tectus.. 62. Fusus. 
c. Teste siphon brevis. Peritrema postice conforme. 
Apertura ad dextram emarginata........ 63. MANGELIA. 
Apertura ad dextram perfecta.......... 64. Brxa. 
*EX Testa alté turrita. 
Stirps 4. Apertura anticé in alam lobatam dilatata, ad sinis- 
tram canaliculata. 
Testa alté et acuté elevata; anfractu ultimo 
in alam digitatam dilatato .......... 65. APPoRHAIS. 
Stirps 5. Apertura, anticé in siphonem brevem recurvum pro- 
ducta, anticé simplex. 
Testa conicé et alté elevata; apertura ad 
sinistram paulo volutata et deflexa.... 66. CeRITHIUM. 
The shell elevatedly spiral, rarely involuted. The aperture 
on the left side, (except in the heterostrophe or reversed shells), 
is produced into a simple or covered canal, forming a siphon. 
The operculum is horny. The mantle on the left side anteriorly 
is produced into a respiratory siphon, which fills the siphon of 
the shell. The mouth is produced into a flexible, rounded, re- 
tractile rostrum or beak, which is formed of two integuments. 
