REPORT ON THE LAMELLIBRANCHIATA. 87 



iuternal ligament. The anterior is narrow, and diverges slightly towards the front, the 

 posterior being twice as thick, triangular, and directed towards the opposite end. The 

 lateral grooves are broad and deep for the reception of the raised corresponding teeth 

 in the opposite valve. In this there is but a single cardinal, equalling in stoutness the 

 large one in the right valve, and fitting in between it and the smaller one. The inner 

 surface of the valves is glossy in the main, but towards the upper part it becomes dulled 

 and roughened by a minute corrugation, granulation, and pitting. The muscular impres- 

 sions are not clearly distinguishable, but ajipear to be moderately large. The siphonal 

 inflection is very broad and deep, reaching far beyond the centre of the valves. 



Length 16f mm., height 10, diameter 5. 



Habitat. — Station 210, east of the Island of Panay, Philippine Islands, at a depth of 

 375 fathoms ; blue mud. 



Semele (Abra) regularis, n. sp. (PI. V. figs. 4-46). 



Testa elougato-ovata, tenuissima, pellucida, polita, vitrea, paulo insequilateralis, 

 aUquanto convexa, utrinque acute rotundata, striis tenuissimis concentricis sculpta. 

 Umbones parvi, paululum supra margincm dorsalem exerti, paulo pone medium collocati. 

 Margo dorsi leviter convexus et declivis ; ventralis late regulariterque arcuatus. Dentes 

 laterales valvse dextrae, elongati, lamellares, ab apice fere sequidistantes. Cardinales duo 

 divergentes, iufequales, postico majori triangulare. Fossa ligament! angusta, elongata, 

 profunda. Sinus pallii profuudissimus, antice late rotundatus. 



Of this fragile shell only a single right valve was dredged. It is excessively thin, 

 semitransparent, glossy, and sculptured with extremely fine lines of growi;h. It 

 idso exhibits towards the ventral margin a few short radiating striae, which, however, 

 may be merely accidental scratches. It is of an elongate ovate form, acutely rounded at 

 both ends, rather convex, somewhat inequilateral, the anterior side being rather longer 

 than the posterior. The dorsal margin is gently convex on both sides and moderately 

 sloping, the ventral being broadly and regularly curved. The beaks are small, a little 

 post-median, and slightly raised above the hinge-line. The two cardinal teeth of the 

 right valve are of unequal size, diverging, the posterior being nearly twice the size of the 

 front one, stout and triangular. The laterals are long, slender, prominent, about equi- 

 distant from the apex, and separated from the outer edge by a deep groove. The cartilage- 

 pit is very long, deep, and narrow. The paUial sinus is likewise very deep, broadly 

 rounded in front, and extends about three-fourths of the total length across the valve. 



Length 7 mm., height 4f, diameter of valve If. 



Habitat. — Station 185b, east of Cape York, North Australia, in 155 fathoms; coral 

 sand. 



