BASILISSA. 425 



Longitudinals there are of these on the last whorl about 120 ; 

 flexuous, marking the lines of growth, rather stronger, more regular 

 and more distant than the spirals, which run over the top of them 

 and form little white nodes at the crossings. The intersections of 

 these two systems cut the whole surface into rhombic reticulations, 

 whose breadth is about O'Oll and their height 0*006. The longi- 

 tudinal threads themselves are about 0*005 and the spirals about 

 0*003 broad. On the base the longitudinals are flattened and 

 spread out into undulations. Color creamy, on a dull polished 

 surface, with a faint nacreous gleam which is pearly within the 

 mouth ; the apex is ruddy. Spire high and conical with slightly 

 concave slopes ; apex broken. On the upper whorls the longi- 

 tudinals are strong, while the spirals are obsolete, except the carinal 

 fillet, which projects bluntly above the suture. Whorls about 14, 

 of very regular increase, very slightly convex, sharply acute-angled 

 at the carina ; on the base, flat at the outer edge and barely convex 

 in the middle, with a slight dip in toward the edge of the umbilicus 

 which is strongly defined. Suture linear, defined by the white 

 carinal fillet, and also on the lower whorls by being very slightly im- 

 pressed. Mouth perpendicular, rhomboidal, the basal and palatal 

 lines being parallel, the other two are somewhat diverging and curved, 

 broader than high. Outer lip sharp and thin, not patulous, not 

 descending, with a shallow open sinus below the suture, then, about 

 the middle of the whorl, it advances with a rounded sweep, retreat- 

 ing sharply across the carina to form the open rounded basal sinus 

 toward the outer edge of the base. Pillar-lip sharp and thin ; it 

 rises from the body a good way within the edge of the umbilicus. It 

 retreats so as to form a sinus, and then it bends over a little on the 

 umbilicus, and it forms a sharp angle projecting into a tooth at the 

 extreme point of the pillar. Umbilicus strong, deep, abrupt, there 

 being on the base only a very slight dip in toward it and it is defined 

 by the white-beaded fillet. Within, besides the two spiral lines, there 

 are slight longitudinal striations, and the inner edge of the whorls 

 twines like a stair case round it, but concealed by the overcurve of 

 the pillar-lip. Alt. *75 in. diam. '65, least '6 inch. ( Watson.) 



The form of this shell connects it with B. alta, B. simplex, and 

 B. munda, and it distinctly has the sinuses of the genus : the layer 

 of nacre is .very faint ; there is, however, a gleam of it through the 

 surface-layer, and within the mouth, in a favorable light and pro- 

 tected from light coming through the shell, there is a distinct 



