1728 THE VOYAGE OF H.M.S. CHALLENGER. 



margins of the two boat-shaped valves dentate nearly in the whole perimeter ; in one lateral border 

 of each valve eleven or twelve very large conical teeth, the largest of which are nearly half as 

 high as the valve. On the aboral hinge of the shell two divergent, very large horns, four-sided 

 pyramidal, acute, straight, at the base perforated by a few large pores. The dorsal horn (of the 

 smaller valve) is somewhat shorter than the ventral horn (of the larger valve). The apical distance 

 of both horns is somewhat greater than their length, and about half the length of the shell. In 

 the half frontal perimeter (along one border of each valve) thirty-two to thirty-four pores, in the 

 half sagittal perimeter thirty-four to thirty-eight, in the half equator thirty to thirty-three. The 

 pores are smaller near the girdle-fissure, irregularly quadrangular, and arranged in longitudinal 

 rows, which are separated by meridional crests, and converge towards both poles of the main axis. 



Dimensions.— Length of the shell (without the horns) 0-24 to 0-26, height 0-20 to 0-22, breadth 

 016 to 018 ; length of the horns 01 to 013. 



Habitat. — Eastern part of the Tropical Atlantic, near the Equator, Station 348, depth 2450 

 fathoms. 



2. Conchoceras cornutum, n. sp. (PI. 124, fig. 16). 



Shell lenticular, strongly compressed on both sides ; proportion of the longitudinal axis to 

 the sagittal and lateral = 4:3:2. Sagittal perimeter ovate, frontal perimeter elliptical, cinctural 

 perimeter spindle-shaped. Free margins of the two keeled valves in the oral third smooth, in the 

 remaining part strongly dentate ; ten or eleven large teeth on one lateral border of each valve, the 

 largest about half as high as the valve. On the aboral hinge of the shell two fenestrated apopliyses 

 which bear two stout, strongly curved horns, like pincers ; the dorsal horn (of the smaller upper 

 valve) is shorter and less curved than the ventral horn (of the larger lower valve). The lips of 

 the mouth (at left on fig. 16) are also unequal, the upper lip emarginate. In the half frontal 

 perimeter of the valve twenty-two to twenty-four pores, in the half sagittal perimeter twenty-eight 

 to thirty, in the half equator twenty to twenty-two. The pores are separated by high parallel 

 crests and arranged in longitudinal rows, which converge towards the aboral hinge. 



Dimensions. — Length of the shell (without the horns) 0'36 to 0"4, height 0'27 to 0-3, breadth 

 0-2 to 0-22 ; length of the horns 016 to 0-22. 



Habitat. — -Tropical Atlantic, Station 338, depth 1990 fathoms. 



Family LXXXIV. Ccelodendrida, Haeckel (PL 121). 



Goelodenilrida, Hueckel, 1862, Monogr. d. Eadiol., p. 3G0. 



Definition. — Ph^odaria with a bivalved lattice-shell, composed of two hemi- 

 spherical valves, a dorsal and a ventral. A conical cupola or a pyramidal galea arises 

 from the apical pole of both valves, therefore at the opposite poles of the sagittal axis. 

 Rhinocanna and freuula wantinff. Three or more hollow radial tubes arise from each 

 valve and are symmetrically disposed. Sometimes their branches form an outer 



