TETHYS CERVINA DALL AND SIMPSON 4I 



face. They are composed of the usual rolled plate with an 

 external, auriform slit. The bases are wide apart being separated 

 by 3.0 mm. distance. 



Internal Anatomy. 



The animal was opened along the median line of the foot 

 by a longitudinal incision, in order to disturb the viscera as 

 little as possible. The peritoneum is colorless, the liver light 

 chocolate, the grey windings of the intestine inclosing it in spiral 

 turns. 



Alimentary System. 



Pharyngeal bulb. The pharyngeal bulb is nearly spherical 

 and slightly elongate, the radula sack projecting from its ventral 

 surface as a prominent, rounded eminence. The salivary glands 

 are long, slender and strap shaped, their relations being similar to 

 Tethys dactylomela and other Aplysiidae. A pair of oblong 

 lateral laminae, placed obliquely, the mandibular plates, (PI. Ill, 

 fig- 15)' guard the entrance of the pharyngeal bulb, being sep- 

 arated above and below by a narrow interval. The extreme width 

 of a mandible is approximately two-thirds of its greatest length, 

 the actual measurements in the individual at hand being 3.00 mm. 

 in length by 1.9 mm. in width. The borders of the mandibles 

 are rounded. Each lamina is made up of a countless number 

 of flexible, nearly straight rodlets with slightly dilated blunt tips 

 (PI. Ill, fig. 16), having a maximum length of 0.09 mm. and 

 a diameter of 0.006 mm., the length decreasing toward the poste- 

 rior border of the lamina, the diameter remaining the same, the 

 rodlet being somewhat flattened antero-posteriorly. The bases 

 of the rodlets are supported by a homogenous horny cuticula of 

 considerable thickness. 



Radula. The radula is of a deep amber color in Its anterior 

 older portion, becoming much lighter posteriorly. It measures 

 5.0 mm. in greatest length by 4.8 mm. in width at its posterior 

 end, tapering, at first gradually, then more rapidly for the last 

 two-fifths of its length to a rounded anterior end. The anterior 

 rows of teeth are incomplete, being worn away and broken by 

 use. The teeth are arranged in 38 rows, the last 15 of which 

 are inclosed in the radula sheath. The number of teeth in each 



