NO. 1700. 



ON THE BARNACLES OF PERU—PIL8BRY. 



71 



and almost always very deeply eroded, dull and gray, with little of 

 the original surface remaining on the exterior of either wall or 

 movable plates. The specific characters are most clearly exhibited 

 in the shape of the scuta, or larger opercular plates. 



CHTHAMALUS CIRRATUS Darwin. 



1854. CMliamalwi elrratus Darwin, Monograph ou the Cirripedia, Balan- 

 idje, p. 461, pi. 18, figs. 4a, 4b. 



Localities. — Northeast side of San Lorenzo Island, shore, on rocks ; 

 Pescadores Islands, on Balanus psittacus Molina (R. E. Coker). 



The barnacle is small, diameter of base 10 to 13 mm., and usually 

 low, irregular in contour, the individuals often crowded, forming a 

 crust on the rocks. Wlien free the peripheral portion is costate and 

 strongly crenated or toothed at the edge. The upper part of the wall 



FlO. 



-Chtham.\lits cireatu.s. inside views of tergdji and scutdm enlarged, and 

 group of three entire animals, nat. size. 



and the opercular plates are deeply eroded, dull gray. The sutures 

 are obliterated. The orifice is rather large. The interior is dull 

 purplish. 



The sutures of the opercular plates form a figure the shape of the 

 Greek letter *. The scutum is triangular, the articular groove mak- 

 ing a deep notch at the tergal side. Articular ridge well developed. 

 The adductor muscle impression is very deep. The tergum has a 

 ridge inside along the upper and scutal margins. The baso-carinal 

 angle projects. There are two very short crests for the insertion of 

 the depressor muscles. 



This species is most readily recognized by the shapes of the terga 

 and scuta, both differing conspicuously from those of C. scahrosvs. 

 According to Darwin, large specimens from Coquimbo and Val- 

 paraiso have a height of 1 inch with a basal diameter of half as much. 

 All of those I have seen from Peru are depressed. 



