THE SESSILE BARNACLES. 103 



BALANUS CONCAVUS PROTEUS Conrad. 

 Plate 22, figg. 3-3c. 



1834, Balanus proteus Conrad, Journal of the Academy of Natural Sciencea of 

 Philadelphia, vol. 7, p. 134 (Jamea River, Suffolk; Yorktown, Virginia). 



1845. Balanus proteus Conrad, Fossils of the Medial Tertiary of the United 

 States, No. 3, p. 77, pi. 44, fig. 1 (Prince George Co., Virginia). 



A large, solid, conic form, with small, angular, and deeply toothed 

 orifice, and very strong, unequal ribs, resembUng the geniculatus form 

 of B. halanus. The summits of the radii slope steeply. The opercular 

 valves are tliin and frail for so solid a barnacle. Scutum with much 

 -finer, more delicate external sculpture than Crag concavus, the longi- 

 tudinal grooves shallower; tergal margmal inflection narrower; artic- 

 ular ridge delicate. Adductor ridge usually somewhat better devel- 

 oped than in Crag concavus; and there is a shghtly raised edge to 

 the depressor muscle pit. The tergum is wider than that of typical 

 concavus. It commonly grows on oysters or the large Pectens, often 

 in very fine groups. 



B. c. proteus seems to have persisted to the Pliocene in a somewhat 

 changed form. A barnacle from the Floridian Pliocene of Alligator 

 Creek is very sohd and strong ; aperture contracted, but less than in B. c. 

 proteus; parietes ribbed throughout or near the apices only. Oper- 

 cular valves not seen. Diameter 50 to 60 mm., height somewhat 

 greater. 



BALANUS CONCAVUS CHESAPEAKENSIS, new subspecies. 

 Plate 22, figs. 1-lc. 



1890. Balanus convesMs, American Naturalist, p. 771 (presumably an error for 



concavus; no description). 

 1904. Balanus concavus Bronn, Martin, Maryland Geological Survey, Miocene, 



p. 94, pi. 33, figs. 1-6; pi. 34, figs. 1-7. 



Type.— 'No. 1143, A.N.S.P. 



Distribution. — St. Marys and Choptank formations, Miocene of 

 Maryland. 



A large, soHd barnacle, with small orifice, the parietes having few, 

 strong ribs near their apices, becoming broader and lower downward 

 until they disappear, and with a peculiar fine sculpture as if shriveled ; 

 radii simken, slithke in the lower part. 



Diameter 57 mm., height 44 mm. 



Scutum having fine, unequal, longitudinal striae over the rather 

 low and wide growth-ridges, about as in B. c. proteus. Ridges of the 

 inner face more developed than in B. concavus or proteus; adductor 

 ridge long, high in the middle. The large and deep pit for the lateral 

 depressor muscle has a strongly raised bordering ridge, which is 

 parallel to the adductor ridge, and nearer it than to the tergal margin. 



