128° 
Geotria australis, GRAY. 
Diagnostie Characters of the Genus and Species. 
The genus Geotria is distinguished from the two other well- 
established (according to PLarE 49) Petromyzont genera of the southern 
hemisphere—Mordacia and Exomegas—by the combination oft he fol- 
lowing characters: a large gular sac is present in the adult and the 
suctorial funnel is greatly developed (see fig. 5); two dorsal fins 
equal in length, the hinder of which is not fused with the tail fin 
(see fig. 5); the anus is situated at the level oft the front end of the 
second dorsal fin; the lip border of de buccal funnel carries an inner 
series (1.8.8. P.) of numerous frayed leaf-like processes (see figs. 
8 and 9) and an outer series (0.8.8.P.) of small tentacle-like cirri 
(see fig. 8); a very large maxillary tooth is present in the form of 
a transverse plate carrying two large outer teeth and two smaller 
inner teeth, these last being half as broad as the outer (see figs. 8, 11); 
the funnel or disc teeth are all arranged in radial rows, the biggest 
being innermost. It is probable that, as shown by Dexpy and OLLIVER 
(42), every species of the genus Geotria passes through three distinet 
phases in its life-history—the Ammocoete stage; the adolescent or im- 
mature sexual Velasia stage (originally described as a distinct genus 
by Gray (43) in 1851 but placed by GÜNTHER (44) as a species of 
Geotria in 1870; OsıLey (48) in 1896 erroneously re-elevated Velasia 
to generic rank) similar to the adult but possessing no gular pouch; 
and the adult or pouched stage. There are said to be three distinct 
species of Geotria—G. australis from Australia and South America, 
G. chilensis from the same two regions and New Zealand, and G. 
stenostomus from New Zealand and Tasmania—but as PLarEe himself 
suggests, it is doubtful if these three species are well founded; it is 
indeed almost certain that G. australis and G. chilensis are one and 
the same (figures of both are given by Hurrox 46), the latter being 
merely a younger stage of growth of the former (Denby and OLLIvER 42 
and Smirr 50, who also states that the genus Exomegas cannot be 
distinguished from Geotria) and it is difficult to understand in what 
essential particulars G. stenostomus differs from G. chilensis (WarrE 51). 
The characters of the adult G. australis are thus those-of the genus, 
to which certain others may be added:—the mandibular tooth or lamina 
is low and slightly sinuous (see figs. 8, 11); between the mandibular 
tooth and the lower lip the disc teeth consist of a single row only 
