8 8 Memoir Sears Foundation for Marine Research 



when latter is closed, its length from center of cloaca more than half as great 

 as distance from cloaca to snout; teeth with one cusp only. 



Torpedo Houttuyn 1764, p. 90. 

 lb. Mouth narrow, not widely distensible, protractile as a short tube; upper and 

 lower jaw cartilages bound together at each corner of mouth by a labial cartilage 

 of two triangular elements (p. 108)," the cartilages rigidly articulated one with the 

 other; integument bearing the tooth bands only loosely attached to jaw cartilages. 

 3 a. Nostril not divided into two separate apertures by a cross bridge midway of 

 its length; teeth extending well out onto upper and lower lips and largely 



Figure 20. Hypnos subnigrunt, female, about 185 mm 

 long, from Port Jackson, New South Wales (Harv. 

 Mus. Comp. Zool., No. 984). Nostrils and mouth, 

 about 1.5 X. 



exposed when mouth is closed; lateral terminations of tooth bands not marked 

 by deep cross furrows. 



4a. Eye minute, sometimes entirely concealed by overlying integument, 

 hence doubtless blind; sides of tail without longitudinal membranous 

 fold, at most with a low fleshy ridge. 



Benthobatis Alcock 1898, p. 126. 

 4b. Eyes normally developed and functional; each side of tail with a thin 

 ribband-like longitudinal fold. 

 5 a. Nasal curtain much broader than long. 



6a. Posterior margins of pelvics not joined across base of tail in a 

 continuous arc by a membranous connection. 



Narcine Henle 1834, including 

 Narcinops Whitley 1940, p. 107.^^ 



37. The presence of these labial cartilages is easily detected by touch in specimens not hardened too much in preservative. 



38. See p. 107, footnote io8. 



