168 



BULLETIN 93, UNITED STATES NATIONAL MUSEUM. 



Is a tuft of fine spines. The segments of these three pairs of cirri are not much 

 protuberant in front. The segments of the posterior cirri have four, or five, or 

 six pairs of spines. Penis, with a straight, sharp, short point on the dorsal 

 basis. 



It may be added to Darwin's description of the cirri, quoted above, 

 that there is a small area of short spinules on part of the segments 

 of the third pair of cirri, and in some large forms there are a few 

 on the fourth cirri also. The peduncle of the third cirrus is very 

 broad. There is a group of small slender spines below the upper 

 great pair of the maxilla, and another group of small spines just 

 above the lower angle. These are characteristic of all forms of the 

 species examined (fig. 50). 



Bruguiere describes this barnacle as depressed-conic, smooth, 

 crenulated or sometimes plicate toward the base. This is a common 

 English form, figured on plate 39, figure 1 from specimens on a 

 potsherd, mouth of the Exe River. The diameter is usually up to 

 16 or 18 mm. The opercular valves of one of these patelliform speci- 

 mens are draAvn in figure 51, , b. 



D 



FIG. 51. BALANUS CRENATUS. a, l>, SCUTUM AND TEUGUM OF AN UNWORN PATELLIFORM 



INDIVIDUAL FROM EXMOUTH, SOUTH I)KVON. c, (I, SCUTUM AND TERGUM OF A RUGGED, 

 DEEPLY CORRODED INDIVIDUAL FROM EXMOUTH. 



A rugged, deeply- worn individual, in which the articular ridges 

 are more broadly reflexed, supplied the valves drawn in figure 51 <?, d. 



These specimens will serve to show the typical form; but it will 

 be understood that there is great variation among English specimens, 

 from depressed and quite smooth to cjdindric and very rugged. 

 Various forms from American waters differ more or less. In some 

 cases, as on the Newfoundland Banks, the divergence is probably 

 racial; yet as I have not seen deep-w T ater specimens from Europe 

 I merely note here the chief American forms, leaving the question 

 of racial differentiation in abeyance. 



Greenland specimens are rather large and solid, cylindric, short 

 or long or tubular, often having rude, rounded ribs distally, vary- 

 ing from weak to nearly as strong as in the form of the Newfound- 

 land Bank. The scutum, as usual in long specimens, is rather 

 lengthened; the upper part roughened inside in a lot from Davis 

 Strait (pi. 39, figs. 4, 4<z), but smooth in those from Inglefield Gulf 

 (pi. -40, figs. 4, 4 ) . See also fig. 52a,, 5. 



