KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 52. N:o (6. 67 
direction; on these the muscles of the pharyngeal bulbus are inserted. No denticu- 
lation at all exists on the jaws, which have a homogenous lamellar structure with 
thickenings at the ridges. 
The radula (fig. 20) has the formula 45 X 1.1.1; it measures 0.5 mm in breadth. 
The breadth of the median tooth is 0.18 mm, its length is 0.09 mm, the lateral tooth 
has a breadth of 0.14 and a length of 0.11 mm. All the teeth are of a light yellowish 
colour. They consist of a strong central spine and lateral denticles, in the median 
tooth at both sides of the spine, in the lateral ones at the median side only. The 
number of denticles is somewhat variable: 7—10 in the lateral teeth and 9—11 on 
Fig. 21. Anatomy of Madrella ferruginosa A. & H. a. anus; 
c. g. cerebral ganglia: d. liver duct; g. hermaphrodite gland; 
h. heart; 7. pharyngeal bulbus; I. liver diverticula ; m. stomach ; 
n nephridium ; o eyes; rh. rhinophores; u. nephridial pore; 
3 male, 9 female genital orifice. 
each side of the median ones. In each tooth the denticulated part forms a semi- 
circular arch or comb, the innermost pines in it being the longer ones in the central 
teeth, and the most lateral ones in the lateral teeth. Seen from behind, each tooth 
has a somewhat shield-like, slightly convex, upper surface. 
Behind the pharynx a short and narrow oesophagus leads to the stomach, which 
has a somewhat curved shape (fig. 21 m.) and lies towards the left. From the stomach 
the intestine emerges and runs over to the right side, then over the mucus gland 
and the hermaphrodite gland again over to the left side, from where the rectum 
bends back again and leads in a slight curve to the anus (a.). The intestine is, 
