SPECIAL ANATOMY. 199 
Helix ; H. alloJabris, H. thyroidus, H. sayi, H. tri- 
dentata, H.fallax, H. palliata, H. ligera, IT. intcrtexta, 
H. supjoressa, H. auriculata, H. elevata, H. profunda, 
H. concava, H. fidiginosa, H. perspectiva, H. alternata, 
H. cellaria, H. exoleta, H. multilineata, H. hirsuta, H. 
solitaria, H. dentifera, M. arborea, H. pulchella, H. 
berlanderiana, IT. gularis, H. injlecta, H. texasiana. 
Bulimus ; B.fasciatus, B. decollatus, B. virgulatus, 
B. dealbatus, B. caribbceorum. 
Pupa ; P. incana. 
Succinea ; S. obliqua. 
Glandina ; Gt. truncata. 
Chapter i. — general remarks upon the exterior form 
and structure of the terrestrial naked gastero- 
PODA. 
Upon examining a Limax or an Arion, we find it com- 
posed of a thick, vermiform body, with a broad, ribbon- 
like, pedal disc, running the whole length of its inferior 
surface. The anterior, obtuse extremity forms the head ; 
and from it protrude four retractile tentaculse, upon the 
outer side of the tip of the two superior, or longer of 
which, is placed the eye. The mouth is situated at the 
antero-mferior part of the head ; and immediately below 
it is a deep depression, or blind sac. The posterior part 
of the body forms the tail, and is acute. Upon the 
antero-superior part of the body is placed the mantle, 
which covers the pulmonary chamber, and contains within 
