Mr. W. H. Benson on the Pteropodom Genus Hyalaea. 23 



The slight characters assigned to H. tridentata in Gray^s ' Cat. 

 Brit. Mus/ will apply to either form; and those given for H. 

 affinis, D'Orb.,in the same work, are, as far as they go, applicable 

 partly to both — noticing the narrowness of the protruded labrum 

 as well as the emargination at the end- According to Souleyet, 

 the darker colour and smaller size of H. affinis are its chief 

 characteristics. The colour is quite immaterial, as I find all va- 

 riations of it in the larger type. In the smaller shell the apex of 

 the labrum is occasionally flexuose, but it does not present the 

 decided emargination so conspicuous in the other form. 



Hyalaa uncinata, Rang. 

 Three different varieties in size occurred, — the smallest in the 

 northern tropical Atlantic, the medium-sized in the tropical por- 

 tion of the Indian Ocean, and the largest (measuring 9 mill, in 

 length and 5^ in breadth) in the Bay of Bengal, about 15^° N. 

 lat., and in the Indian Ocean in S. lat. 6^° and E. long. 83^°. 



Hyalaa globulosa, Rang. 



I consider this species, with reference to Bang's figure and 

 Souleyet's description, to be the same as the Philippine H. {Ca- 

 volina) Pisum, Morch, Zeitschr.1850, notwithstanding Souleyet's 

 character " superne quinque-costata," and Morch's " inferne 

 convexa, medio sulcis 3 divergentibus," which would attribute 

 only three ribs to the part which he regards as the lower, but 

 which is the superior side according to Souleyet's view. This 

 difference is easily reconciled by the probability that an incon- 

 spicuous elevation on either side, connected with the prominence 

 which borders the fore part of the lateral rift, was regarded by 

 Souleyet as a rib, and rightly disregarded, on the other hand, 

 by Morch, — the two deep furrows between the three central ribs 

 being alone conspicuous in Bang's figure No. 18 of plate 2, as 

 contrasted with the five conspicuous ribs in the adjoining figure 

 No. 14 of H. uncinata. It is also evident that Rang's figure 

 17 was taken from a specimen oi H. globulosa with an imperfect 

 labrum, and deficient in the perpendicular inflexion in front of 

 the aperture noticed by Souleyet. 



H. globulosa was taken on seven different occasions, in De- 

 cember 1834 and January 1835, from 2° S. lat. and 88° E. long, 

 to the head of the Bay of Bengal, and in greater abundance on 

 the southern side of the Equator than on the northern. In 1846 

 it was captured on two nights, near 5° S. lat. and 82^° E. long., 

 where calms and squalls alternated. 



Hyalcea gibbosa, Rang. 

 Souleyet has confounded this form with the larger calceolate 

 species, H. flava, D'Orb., and refers to the figure of the latter 



