THE SESSILE BARNACLES. 267 



CHELONIBIA CARETTA (Spengler). 

 Plate G3, fi.^s. 5, 5a. 



1790. Lcpas caretta Spengler, Skriftei* af Naturhist, Selskabet, vol. 1, 



p. 185, pi. 6, fig. 4. 

 1825. AfttroleiHin tcHtndinnrin Gray, Annals of Philosophy, vol. 10, p. 105. 

 1840. Bnlanus cheli/try petes Hinks, Anuals of Natural History, vol. 5, pp. 



333-4. 



. Coronida siileata Chentt, Illustrations Conchyliologiques, pi. 1, fig. 1. 



1854. Chclonohia eareHa Darwtn, Monograjih, p. 394, pi. 14, fig. 2. 



According- to Darwin — 



The descending sheath and radiating septa are of very variable thickness and 

 have their basal edges finely dentated. The septa are not continuous from the 

 circumference to the sheath in i;nbroken plates, but are irregularly divided into 

 separate, often short, portions and even occasionally into mere points. The 

 sheath differs from that of the other two specimens in having loopholes for the 

 entrance of ribbons of corium only on the eight lines of siiture, and not, with 

 rare exceptions, in the middle of each compartment. This is evidently due to 

 fewer filaments of corium being here sufficient to siipply the less deep inter- 

 spaces between the radiating septa, for in this species there are no flattened 

 cavities or tubes running far up the shell. The inner lamina of the walls can 

 not be here distinguished, for a solid, flat calcareous surface extends from the 

 circumference between the radiating septa to the sheath. The sheath, had it 

 not been from the light thrown on this part by the other species, would have cer- 

 tainly been mistaken for the inner lamina of the walls. TJtc ahsenee of the 

 fldttened cavities or tubes extendinfj up tJie parietes seems to he the least vary- 

 i)ig eliaracter and serves to distinguish this species from those worn and massive 

 specimens of C. testndinaria, which have narrow and not-notched radii. 



The opercular valves hardly present any essential difference, compared Avith 

 those of the other species, but the occludent margin of the scutum is apt to be 

 more sinuous and its rostral end bUniter and sciuarer. The carinal end of the 

 tergum is also squarer than in any conmion variety of C. testndinaria, the 

 external furrow or spur near the carinal margin is very indistinct, and even 

 sometimes is quite absent. 



Distrihutlon. — Darwin had tliis species from the west coast of 

 Africa and northern Australia. Doctor Wehner reports i t from Yene- 

 ziiehi, Massaim, and Torres Strait. The Paris Museum has speci- 

 mens from Cape of Good Hope and Saigon. Specimens are in the 

 collection of the Academy of Natural Sciences, Philadelphia, from 

 St. Thomas, West Indies, taken by Robert Swift, and from a logger- 

 head turtle from DelaAvare Bay, New Jersey, taken by m5''self. These 

 examples are ver}^ small and fiat, 13 mm. long, and nearly covered by 

 the shell of the turtle. Ecjually small examples of C. festudinarla on 

 the same turtle were not at all embedded. Those in the United States 

 National ISIuseum are from " East Indies," I. Lea collection, and 

 Cape Frio, Brazil, collector not recorded. It appears to be chiefly 

 tropical. Records fi-om the central and eastern Pacific are lacking. 



