Mr. W. H. Benson on the Pteropodous Genus Hyalsea. 27 



Ocean, — on the last occasion in abundance. It occurred also 

 to the south of Madagascar, in 1846. Souleyet notes it as not 

 common, although found in all seas. I did not notice the variety 

 to which he alludes. 



Hyalaa inflexa, Lesueur. 



I took this species only once in the South Atlantic, where a 

 single specimen was met with, about 17° S. lat. and 27° W. long., 

 on the 24th of October, 1834. Souleyet states that it has also 

 been found in the Mediterranean and Pacific. 



Hyal(sa laevigata, D^Orb. 



A scarce and singular little shell, included by Gray in Diacria, 

 which escaped observation in 1834-35. The sole specimen 

 captured in 1846 entered my towing net, with the minute variety 

 of H. quadridentata , in 3° S. lat. and 83° E. long. The dorsal 

 surface has the central elevation noticed by Souleyet and omitted 

 by D'Orbigny in his description. 



Hyalcea 3-spinosa, D'Orb. 



A Diacria of Gray. Of the ordinary variety'', two sizes (one 

 being of very inferior magnitude) as well as two forms were 

 taken, — one having the lateral spines projecting at the sides 

 nearly at right angles to the long posterior mucro; in the other 

 they are slightly inclined backwards at various angles. These 

 two varieties are figured in plate 3 of Hang and Souleyet's 

 work. They were found on seven different occasions, in 1834, 

 in the North and South Atlantic; in the Southern Ocean about 

 39° S. lat. and 33*^ E. long., where the species occurrecT in the 

 greatest number ; and in the Indian Ocean between 7i° and 8^ 

 S. lat. and 86° and 86^° E. long. In 1846 it was captured south 

 of Madagascar. 



Besides these shells, a third aberrant form {H. mucronata, 

 D'Orb.) appeared more rarely. It is of considerably greater 

 magnitude, and is distinguished from the variety of H. trispi- 

 nosa, in which the spines are most inclined backwards, by the 

 position of the lateral spines and the stronger transverse sculp- 

 ture on the venti'al face. There is no figure answering to it in the 

 plates of Rang and Souleyet^s work, but Souleyet pronounces it 

 to be merely a larger and flatter variety. Two specimens were 

 taken in the Southern Indian Ocean between 31° S. lat. and 83° 

 E. long, and 29^° S. lat. and 84° E. long., in a tract where the 

 smaller kind was absent. The spines take their origin further 

 back on the shell, not near the centre of the broad part as in 

 the type of H. trispinosa: the angle formed by them with the 

 central mucro will be found to be one of 33°, and in a specimen 



