KLMIMUS KINGII. 349 



Shell smooth, gray or dirty tohite : radii broad, smooth- 

 edged : scutum without an adductor ridge ; tergum with 

 the spur distinct from the basi-scutal angle : scutum and 

 tergum sometimes calcified together. 



Hab. — Tierra del Euego, Falkland Islands, Cliiloe. Attached to tidal rocks 

 and sometimes to floating timber ; Mus. Brit., Darwin, &c. 



General Appearance. — Shell fragile, either steeply conical with a 

 large orifice, or sub-cylindrical ; surface smooth, grayish or white, w r ith 

 large portions covered by pale brown epidermis. Radii broad with 

 their summits oblique, smooth, slightly arched, exhibiting a large sur- 

 face of the alse. The alee usually have their summits much less 

 oblique than those of the radii ; the portion added during diametric 

 growth is of a dead white colour. The growth ridges on the scuta are 

 very little prominent, and are crossed by a very obscure band of 

 blueish-gray. The largest specimen which I have seen was *8 in basal 

 diameter, and the longest cylindrical variety '55 of an inch in height. 



The Scuta are remarkable for not having any adductor ridge or 

 crests for the depressor muscles ; the articular ridge is prominent, but 

 it is short, not extending down half the valve. I have mentioned 

 under the genus, that in many specimens at the Falkland Islands the 

 scuta and terga were calcified together. 



The Terga are rather small : the basal margin on the carinal side of 

 the spur is always hollowed out, but to a very variable degree, as may 

 be seen in the three figures (G c — 6 e) ; this margin is generally dentated 

 with one or two little points; and an inner lamina of shell sometimes 

 depends beneath the outer lamina, to which the opercular membrane 

 is attached, as may be seen in the figure (6 d) of the external surface 

 of the valve. The crests for the depressor muscles are well developed. 

 The tergal margin is broadly inflected, and the articular ridge promi- 

 nent, making the articular furrow deep. The spur is rather narrow, 

 and is either (6 d, 6 e) bluntly or sharply pointed. The basal margin 

 on the scutal side of the spur, is hollowed out, but to a variable 

 depth. 



Structure of the Parietes and Radii. — The parietes are thin; at their 

 internal basal edges they are finely striated in longitudinal lines. The 

 radii are solid, with quite smooth edges ; they are generally covered 

 by the epidermis. The sutural edges of the alee are likewise smooth, 

 these are added to largely during the diametric growth; and their 

 summits, as already stated, are much less oblique than the summits of 

 the radii. The internal surface of the shell is smooth, and is tinted 

 pale dull purple. The lower edge of the sheath can hardly be said to 

 be free. The carinal margins of the compartments project a little 

 inwards. 



Mouth: the labrum is deeply notched, and supports five little teeth 

 on each side ; the palpi are thickly clothed with spines on their inner 

 sides ; the mandibles have five or only four teeth : the maxillae are 

 notched, and the outer maxillae bilobed. 



