THE SESSILE BARNACLES. 57 



the posterior ramus protuberant. Besides the usual long spines, the 

 distal borders of the segments bear minute multifid scales. 



Cirrus ii has 15 and 12 protuberant segments, posterior ramus 

 shorter by 5 segments. 



Cirrus iii is about one-third longer than ii, with rami of 14 and 13 

 somewhat protuberant segments, the posterior ramus shorter by 4 

 segments. They have series of short, erect spinules along the distal 

 borders of the segments. 



Cirri iv to vi are nearly similar, composed of a gieat number of 

 short segments, which bear three pairs of long and a fourth of short 

 spines. There are tufts o f small spines on the anterior edge, between 

 the spines of the pairs. A regular row of erect spinules borders each 

 segment distally, wanting on some of the ill-defined basal segments. 

 The anterior distal angles of the pedicel are also spinulose. The 

 median segments of cirrus vi are about twice as wide as long (fig. 

 9o ). Cirrus vi is about 23 mm. long. 



Balanus tintinndbulum tintinnabulum (Linnaeus) is known in North 

 American waters only as a frequent immigrant on ships. I do not 

 know that it has anywhere established itself in our fauna, but we 

 have no knowledge of the barnacles of the Gulf ports, where such 

 introduction would be expected to occur, if anywhere. The natural 

 habitat of the race remains to be defined, and the inquiry is difficult, 

 because specimens from ports all over the world find their way into 

 museums, without data showing whether they are part of the local 

 fauna or from ship's bottoms; moreover, it is likely that some forms 

 recorded as var. corn-munis will prove to be separable races. It has 

 not been found in any Antillean or North American Tertiary or 

 Pleistocene deposits. 



Figures 1 le and the above description were drawn from speci- 

 mens taken from a ship which arrived at Philadelphia from Hongkong 

 and Java. They were associated with B. t. zebra and B. t. occator, 

 but no intermediate or transitional forms were seen. The cylindric 

 form with larger orifice, is prevalent in other lots, particularly those 

 standing crowded. 



The United States National Museum contains numerous specimens 

 referred to B. t. tintinnabulum, chiefly collected from ships in English 

 and American ports; others from tropical localities and New Zealand 

 are without opercular valves, and therefore of uncertain subspecific 

 identity. 



BALANUS TINTINNABULUM ZEBRA Darwin. 



Plate 10, figs. 2 to 3. 



1851. Balanus tintinnabulum, var. zebra DARWIN, Monograph, etc., p. 195, pi. 1, 

 fig-<7- 



Form conical or somewhat tubular ; livid purple or dark livid purple, 

 with snow-white ribs ; radii wide, colored ; sheath madder Irown. Sum- 



