126 BULLETIN- 93, UNITED STATES NATIONAL MUSEUM. 



resulting buoyancy can hardly have any useful function. Probably 

 the cells merely occupy superfluous space, due to hypertrophic 

 lengthening of the tube. 



This series contains only the species Balanus gregarius (Conrad), 

 originally described as the type and sole species of the genus Tamio- 

 soma. Conrad seems at first to have considered Tamiosoma a 

 Rudistid moUusk, and in 1864 he placed its species in the genus 

 Radiolites. Gabb, in 1869, took a similar view, looking upon it as 

 a member of the Hippuritidse In 1876 Conrad recognized the true 

 nature of the fossil, stating that its structure does "not differ essen- 

 tially from Balanus Isevis Brug." Dr. W. H. Dall (1902) reached the 

 same conclusion. 



BALANUS GREGARIUS (Conrad). 



Plate 28, figs. 1-3; plate 29. 



1856. Tamiosoma gregaria Conrad, Proe. Acad. Nat. Sci., Phila., p. 315. 



1857. Tamiosoma gregaria Conrad, Pacific R. R. Report, vol. 6, p. 72, pi. 4, 

 fig. 18. 



1857. Balanns estrellanns Conrad, Pacific R. R. Report, vol. 7, p. 195, pi. 8, 



fig. 1. 

 1864. Radiolites gregaria Conrad, Proc. Acad. Nat. Sci., Phila., p. 214. 

 1869. Tamiosoma gregaria Conrad, Gabb, Geological Survey of California, 



Paleontology, vol. 2, p. 61, pi. 18, figs. 22a.-d. 

 1876. Balanus H. estrellanus Conrad, Proc. Acad. Nat. Sci., Phila., p. 273. 

 1902. Tamiosoma gregaria Conrad, Dall, Science, vol. 15, p. 5 (^Balanus). 



Distribution. — Miocene of California : Estrella ; Santa Marguerita 

 ranch, northeast of San Luis Obispo ; Tulare Valley (Gabb) . Salinas 

 Valley, Monterey County (Homer Hamlin). 



In its typical form (pi. 29) this barnacle is columnar or cylindric, 

 "with the basis lengthened, occupying nearly three-fourths of the 

 total length ; not contracted at the orifice. Externally the basal por- 

 tion of the tube has low, rounded, unequal, and irregular longi- 

 tudinal ribs; the compartments are probably almost smooth, but in 

 specimens at hand they are so much corroded that the external 

 sculpture, if any, is not shown. The parietes are porous ; radii nar- 

 I'ow, and apparently rather deeply sunken if the parietes were not 

 eroded. The sutures are marked by ribs internally. The sheath is 

 from a third to nearly half the length of the compartments, and has 

 a somewhat depending lower edge. 



The basis consists of two parts: a disk-like basal plate (pi. 28, 

 figs. 1, la), which is rather thick and almost solid, but showing a 

 few pores in places, and many in the peripheral part. It seems to he 

 attached hy a small suhcentral point only, but this may be due to 

 the small size of the supporting object of these specimens, which 

 is not preserved with any of them. Externally the basis is rough- 

 ened with irregular concentric ridges and with cavities apparently 



