68 OPISTHOBRANCHIATA OF BRAZIL 



These mandibular plates are made up of slender closely 

 set blunt rodlets, longest in front and decreasing in length toward 

 the posterior border. Those of the anterior portion range up to 

 0.096 mm. in length (PI. XII, fig. 59), and decrease regularly 

 toward the posterior portion, where they are very short (PI. XII, 

 fig. 60), the average diameter of ca. 0.005 ^n"^- remaining nearly 

 the same throughout, the tips of the rodlets being slightly dilated 

 to nearly the same extent also. 



Radiila. The radula is broad and short, deeply grooved 

 longitudinally in the median line, the teeth of one sort, uniform 

 in shape, strongly hooked, and arranged in 26 rows of from 45 

 to 48 teeth in each half row, the rhachis being destitute of teeth. 

 The dental formula may hence be expressed as 45-48 :o :45-48x26. 

 The outermost two or three teeth of each row (PI. XII, fig. 62) 

 are slightly smaller than the remaining teeth of the row, the base 

 of the outermost being about one-third the length of that of the 

 others, the remaining teeth being practically of the same size 

 until the innermost two are reached, which are again somewhat 

 smaller. The average height of a typical tooth (PI. XII, fig. 63) 

 is 0.186 mm., the length of the base 0.15 mm. The general tint 

 of the radula is a faint yellow, deepening posteriorly, while the 

 anterior portion is colorless or nearly so. 



Blood gland. Overlying the buccal mass is the blood gland, 

 divided into two lobes, the largest being thick and rounded, about 

 2.0 mm. in diameter, and is situated in front of, and in contact 

 with the central nervous system. The posterior lobe, immediately 

 behind the anterior one, is much smaller, triangular in form, its 

 base being directed forward, and has a length of 1.5 mm. and 

 a breadth of 0.5 mm. at the broadest end. 



Salivary glands. The salivary glands are long and strap-like, 

 the anterior portion, i.o mm. in width, being coiled upon the 

 posterior face of the pharyngeal bulb. Each narrows to 0.5 mm. 

 in width as it passes through the nerve collar, and extends back- 

 ward, below the viscera ventrally, for about one-half the total 

 length of the animal. 



Esophagus, stomach and intestine. The esophagus is short 

 and wide, ca. 3.0 mm. long by 1.5 mm. in diameter, passing directly 

 downward and backward to the stomach, into which it dilates. 

 The latter organ lies in a deep notch in the anterior face of the 



