ZONITOIDES EXCAVATUS. 135 
The REPRODUCTIVE ORGANS exhibit an OVOTESTIS which is imbedded in the 
digestive gland and placed within the apex of the spire; the HERMAPHRODITE 
DUCT is slightly sinuate, thick and white in mid-course, and leading to the minute 
VESICULA SEMINALIS ; ALBUMEN GLAND elongate, of a clear slate or lilac colour, 
but sometimes greyish-yellow ; OvipUCT sacculate, varying in colour from a light- 
slate to dark-grey ; FREE OVIDUCT not so long as dart-sac, but surrounded and 
concealed by an oval glandular mass of a greenish-yellow colour; SPERM DUCT 
or prostate not closely attached to oviduct, enlarging at base to a white spongey 
KL wv. 
Fic. 1&5. 
Fic. 183. Fic. 184. Fic. 186, 
Fic. 183.—Reproductive organs of Zonrtoides excavatus, x 3, showing the arrangement of its 
constituent parts. 
ot. ovotestis ; 4.d. hermaphrodite duct ; a.g. albumen gland ; s.d. sperm duct ; .s. penis sheath ; 
ov. oviduct ; v. vagina with vaginal gland ; sf. spermatheca with bifid duct; s¢. stylophore or dart sac. 
Fic. 184.—Proximal portion of sexual organs of Zonitoides excavatus, X 10 (from a photograph by - 
Mr. W. Moss) showing the position and character of the calcareous penial plates, the dart, the 
coronal gland, and the bifid spermathecal duct. 
st. stylophore or dart sac showing natural position of dart and coronal gland, c.g@. ; £.s.penis sheath 
with the channeled plates ; vag. vagina ; sf. bifid spermatheca duct. 
Fic. 185.— Upper, lower, and end view of the calcareous penial plate of Zonitoides excavatus (after 
micro-photograph by Mr. W. Moss). 
Fic. 186.—Gypsobelum or Love-dart, showing side and front aspect, X 10, and an enlarged view of 
the head of the dart. 
matter ; SPERMATHECA small and pyriform, of a yellow colour, with a brownish 
nucleus, attached to and imbedded in the upper part of the ovispermatoduet ; the 
stem is grey, very long, and bifureate proximally ; one branch is slender and opens 
into the free oviduct, its junction being concealed by the vaginal glands; the other 
enlarging below joins the penis-sheath near the opening into the atrium, but, 
according to Prof. Pelseneer, does not really open into the penis, but into a closed 
sac or space surrounding the penis and dart-saec; the PENIS-SHEATH is dilated and 
thick below, slender above, passing into the VAS DEFERENS, and interiorly possesses 
the caleareous channeled sheath analogous to that of Cochlicella acuta, but whose 
function is unknown; the DART SAC is long, with a eurved free distal end, and 
bearing a pendant coronal gland beneath the curve; the DART is an exquisite 
and delicate little weapon, and long for the size of the animal, the shaft round and 
slightly twisted, expanding at the base, the apex or free-end slightly compressed 
and dilated ; the degree of twist is variable, but usually forms an are of about 
60 degrees, 
The MANDIBLE or jaw is strongly arcuate and some- 
what crescentic in shape, of an amber colour, with (pit 
delicate wavy striation or sculpture, which runs parallel fe 70 
with the upper and lower margins ; the extremities are Ae IN 
distinetly rounded below and slightly recurved above ; ye ee > 
the upper margin is distinctly incurved in the centre, : Co Gay Eire 
and the lower or cutting margin displays a median, ae: peli e res amas Berry 
somewhat bluntly projecting beak or rostrum, making ° ©07/{*#e excavatusy © M 
the lower and upper margins almost parallel; the elasma is wide and distinet with 
many longitudinal striz. 
