208 BALANJDiE. 



harder shell than the rest of the valve ; hence, when the outer surface 

 and the adjoining scutal and carinal margins disintegrate, this part 

 remains, and so forms the beaked, purple apex. 



Compartments. — The parietal tubes are unusually large in propor- 

 tion to the size of the shell, and run up to the summit without any 

 transverse septa: the longitudinal septa are strongly denticulated. 

 The radii are penetrated by large tubes ; their septa are very strongly 

 denticulated, and the denticuli themselves often subdivide and branch 

 out at their extremities. The sutural edges of the alas are smooth, or 

 with a high power can just be seen to be crenated. The radii are 

 generally very highly developed, so that their summits are even wider 

 than the bases of the parietes ; but, on the other hand, in some few 

 large specimens, the radii are either very narrow or absolutely linear. 

 Tn these latter cases, the diametric growth has nearly or altogether 

 ceased, whilst the walls of the shell have continued to be added to 

 at their bases, their summits at the same time suffering disintegration ; 

 and thus the orifice has increased in size. 



Basis generall} 7 , and occasionally very deeply, cup-formed. An 

 unusually thick cancellated layer in most cases forms the under side 

 of the basis. 



Mouth. — Labrum apparently without teeth, or with very minute 

 ones : mandibles with three teeth, of which the third is thicker than 

 the first or upper one : the fourth and fifth teeth are confluent with the 

 inferior angle. The maxillae have a small notch under the upper pair 

 of spines ; inferior part projecting and supporting two spines, placed 

 one below the other, and equalling in size the upper pair. Cirri : the 

 rami of the first cirrus are unequal by four or five segments ; shorter 

 ramus and both rami of the second cirrus with the segments extremely 

 protuberant : posterior cirri not much elongated, with the segments 

 rather broad, supporting six pairs of spines. 



General Remarks. — This, which is much the largest known species 

 of the genus, ranges from Peru (Arica being the most northern spot, 

 whence I have seen specimens), along the coast of Chile, where it is 

 very abundant at a few fathoms' depth, at least as far south as 

 Southern Chiloe ; it is said by Captain King to attain the largest size 

 at Conception. On the coast of Eastern Patagonia, I dredged up this 

 species from nineteen fathoms, in lat. 49°. In lat. 42° (S. Josef), on 

 the same eastern coast, I found fossil specimens in beds of sand 

 upraised between eighty and one hundred feet. In the tertiary forma- 

 tion at Coquimbo, in Chile, it occurs in the middle bed, associated 

 with the recent B. Icevis, and with various mollusca, all of which are 

 apparently extinct, indicating that the formation is of considerable 

 antiquity. In the living state, on the coast of Chile, it is often 

 associated with B. Icevis. As it frequently adheres to large specimens 

 of the Concholepas, it must sometimes be an inhabitant of shallow 

 water. I have seen one specimen attached to Mytilus Magell aniens. 

 Mr. Cuming believes that about six fathoms is the usual depth at 

 which it lives. Numerous specimens are often congregated together 

 into great masses. Mr. Stutchbury has some interesting specimens 

 which he procured from a ship that had first sailed to Ichaboe, on 



