THE SESSILE BARNACLES. 141 



In the far north, B. rostratus appears in various forms differing 

 from the tjq^ical Japanese form of much warmer waters. Just what 

 status these races, if such they are, will eventually be given, can not 

 be decided until many hundreds are collected and studied. The}'" 

 have no regional differentiation, and it may be a matter of station. 

 At present it seems to me desirable to advertise the differentiation of 

 the group by giving names to the leading forms, which have more 

 tangible characters than the forms of B. halanus. Their most obvious 

 characters are as follows : 



ff\ Transverse septa of parietal tubes extending nearly or quite to the base. 



/('. Radii conspicuously sunken ; about 14 tubes in the rostrum B. rostratns 



J)'. Radii but sligbtly sunlcen ; about IS or more tubes in tbe rostrum. 

 &. Large Alaskan form, diam. GO-TO mm. ; four or five pairs of spines on 



each segment of tlie posterior cirri B. r. alaskensis 



c'. Smaller Puget Sound form, diam. about 38 mm.; at most four pairs of 



spines on segments of posterior cirri B. r. Jtcfrropns 



a\ Transverse septa confined to tbe ujiper lialf of the parietal tubes; usually 

 about 18 tul)es in the rostrum. 

 h\ Radii but slightly sunten. 

 c\ Ratlier thin, wall spinose or somewhat rugose; basis typically concave; 



usuall.v on sponges, sometimes on shells B. r. apertvs 



(^. Large and solid, walls smooth B. r. (Uilli 



ft*. Radii conspicuously sunken, walls thick B. r. suturalis 



BALANUS ROSTRATUS ALASKENSIS, new subspecies. 

 Plate .^8, figs. 4, 4a, 5. 



Type,— Cnt No. 3415, U.S.N.M., from Kodiak, Alaska, 50 feet, 

 collected by W. H. Dall. 



The barnacle is white, conic, very solid, with narrow radii; outer 

 lamina of the wall smooth where preserved, but extensively eroded, 

 exposing the large parietal tubes, which are crossed by many trans- 

 verse septa, down to the hasc. Between the septa, several longi- 

 tudinal threads are seen on the inner lamina. The rostrum has 18 

 tubes. Interseptal ribs on the inside numerous, sometimes G or 9 in 

 one interval. Adductor ridge of the scutum prominent. Both 

 tergum and scutum have a faint pink tint toward their apices. 



Carinorostral diameter, Gl mm.; height, 53 mm. (Kodiak). 



Carinorostral diameter, 70 mm.; height, 4G mm. (Unalaska). 



The labrum in the type-specimen is toothless on one side, with one 

 tooth on the other. ISIandibles as usual in the species. INIaxilla? 

 (fig. 40<7) with the three major spines about twice as long as the 

 others, the discrepancy in size being greater than usual. 



The penis is not so long as in the type of B. r. apertus, but is longer 

 than in B. halanus. 



Cirrus i has rami of 34 and IG segments; cirrus ii nearly equal 

 rami of 19 and 17 segments; cirri iv to vi have five pairs of spines 

 on part of the segments of one ramus, four on the rest and on those 



