CHELOtfOBIA TESTUD1NAR1A. 393 



Lepas testudinaria ; but as Spengler has well discrimi- 

 nated the following species under the specific name of 

 caretta* and Ranzani the third species under patula, the 

 present name may, without question, be retained for the 

 following species. In several respects this species is inter- 

 mediate between C. caretta and patula, but it can most 

 conveniently be described first. 



General Appearance. — Shell strong, globulo-conical, depressed; out- 

 line broadly oval ; surface smooth, generally well preserved, but when 

 disintegrated, upper part finely striated ; colour dead white ; orifice 

 oval elongated, rather exceeding in length one third of the longer basal 

 diameter of the shell. The radii are rather narrow, and deeply 

 depressed ; they have their summits square : their outer lamina, as 

 explained under the genus, on both sides of each suture is in most 

 specimens divided into teeth, the points of which face and touch each 

 other. These teeth or notches give quite a peculiar appearance to the 

 shell, and alone suffice to discriminate this species; they are sometimes 

 blunt and partially obliterated, but it is rare to find a specimen in 

 which some few teeth do not occur in some one of the six radii. I 

 have, however, seen two or three specimens with all six radii perfectly 

 smooth ; in one of these the general shape of the shell, without the aid 

 of any internal characters, almost sufficed to show that it belonged to 

 the present species ; but in another specimen, which had unusually 

 narrow radii, and the whole surface of which had undergone consider- 

 able disintegration, and was consequently striated, could only be dis- 

 tinguished from C. caretta by internal characters. I have seen several 

 specimens having very irregularly shaped compartments, but generally 

 the appearance of the whole shell is highly symmetrical, like a star ; 

 and the genus was appropriately named by old Klein, Astrolepas. In 

 some specimens, in Mr. Cuming's collection, from the Low Archipe- 

 lago, in the Pacific, taken off the toe-nail of a turtle, the shape was 

 almost cylindrical ; the shell almost resembling that of Coronula dia- 

 dema. The largest specimen which I have seen was 2 - 3 of an inch in 

 basal diameter, but only *55 in height. 



Structure of Shell and Radii. — After the full generic description, 

 the only point to which I need allude is, that the radiating, parietal 

 septa, as well as the descending sheath, are much thicker than in C. 

 patula, and that their basal edges can be plainly seen by the naked eye 

 to be dentated with numerous points. The thickness of these plates 

 and of the sheath varies considerably. In C. caretta, I may add, the 

 plates are broken up into many separate points, and in this species 

 the descending sheath is not generally perforated, excepting at the 

 sutures, by loop-holes for the entrance of ribbons of corium. The 



* I am indebted to Dr. J. E. Gray for having guided me to this identifi- 

 cation. 



