24 Mr. W. H. Benson on the Pteropodous Genus Hyalsea. 



(plate 10. figs. 3, 4) as representing Hang's shell, of which no 

 drawing appears in the work. It is suificient to compare speci- 

 mens of the two shells, to become satisfied that Souleyct's state- 

 ment that H. gibbosa is merely an immature H. flava is founded 

 on error. No possible increase of size could convert the per- 

 pendicular lip of H. gibbosa (neai'ly parallel with the anterior 

 portion of the ventral side, and running into an angular apex) 

 into the oblong, scarcely narrowed, and protruding labruui of 

 H. flava, gradually rising as in the smaller shell referred to H. 

 tridentata, nor produce the overhanging form of the anterior 

 ventral portion, so characteristic of D'Orbigny's species. 



H. gibbosa was taken only six times, in November and Decem- 

 ber 1834, and did not exceed two specimens on any occasion. 

 In 1846 eleven specimens were procured by a fellow-passenger, 

 to the south of Madagascar, in one night, and three specimens 

 within sight of the Natal coast. In 1834 the shell occurred 

 between 30° and 31° S. lat. and about 17° W. long., as far as 

 39° S. lat. and 69° E. long.; and the last examples were procured 

 in 4° S. lat. and 87° E. long. 



Hyalcea flava, D'Orb. 



This subcalceolate species did not fall into our nets during 

 the outward voyage in 1834-35. A single specimen was taken 

 in 1846, on the same night as three specimens of H. gibbosa, a 

 little to the south of the embouchure of the Umzimvobo or 

 St. John's River, and within sight of the land of Natal. Its 

 dimensions are 10 mill, in length by 6 in breadth. Those of 

 my largest H. gibbosa are 8 mill, in length by 5| in breadth. 



In addition to the differences above noted, it maybe observed 

 that H. flava has five very flat ribs on the dorsal side, and is 

 delicately and closely striated radiately on both the dorsal and 

 ventral sides, while H. gibbosa is more strongly ribbed on the 

 dorsal face, and the two ribs next to the middle one are each 

 inclined to be divided into two by a longitudinal furrow. The 

 radiate strise on the upper side are scarcely to be distinguished, 

 and on the gibbous ventral side are distant and elevated. 



Hyalaa quadridentata, Lesueur. 



Three varieties of this, the most minute form of the genus, 

 were captured. On the 23rd of October, 1834, I got it in the 

 South Atlantic, about 17° S. lat. and 27° W. long. I find no 

 record of its reappearance until we reached 2° S. lat. and 8b° 

 E. long., where it was abundant, and accompanied us, at inter- 

 vals, nearly to the head of the Bay of Bengal. 



On the 21st of February, 1846, I took nine specimens of an 

 exceedingly minute variety, pellucid, and with obsolete ribs and 



