252 BALANIDiE. 



the United States, sent me by Prof. Agassiz, and with several in three 

 lots from the western tropical shores of South America : yet on close 

 examination I can point out no one distinguishing character, either in 

 the shell or animal's body, excepting the longitudinal hyaline lines on 

 parietes, due to the septa being externally visible. The presence of 

 similar lines is variable in white vars. of B. amaryllis and amphitrite, 

 and they are seen in very young specimens of B. eburneus: hence it is 

 impossible to consider so trifling a character as specific ; moreover, 

 lately I have seen a British specimen with hyaline lines, and some few 

 other specimens in an intermediate condition. Under the head of 

 B. eburneus, I have stated that although that species and B. iwprovisus, 

 which in the West Indies are associated together, are most readily dis- 

 criminated when old, yet when young, they so closely resemble each 

 other that the eye requires much practice to separate them. On account 

 of this species and B. crenatus being sometimes associated together on 

 the shores of England, I have pointed out under B. crenatus, the relative 

 diagnostic characters of the two. The chief affinity of B. i?nprovisiis is 

 certainly towards B. ebwmeus ; but in the narrow, oblique, rounded, 

 and smooth-edged radii, there is a relationship shown to the species 

 in the last section of the genus, such as B. amaryllis, and more espe- 

 cially to the fossil B. dolosus : so close is the resemblance in the external 

 appearance of the shell, and in the structure of the opercular valves, to 

 the latter species, that I for some time did not discover their distinctness. 

 Balanus improvisus has hitherto been overlooked by naturalists, and has 

 probably been confounded with B. crenatus or balanoides. 



Range and habits. — This species, as far as my experience goes, is 

 commoner on the shores of Kent than on other parts of England : the 

 first specimens which I met with, I owed to the kindness of Mr. Metcalf, 

 they were attached to wooden stakes from Heme Bay, together with a 

 single specimen of B. crenatus: I have seen other specimens from near 

 Woolwich, from the Kentish oyster-beds, from Sandwich, and from 

 Ramsgate. The only other British specimens which I have seen are 

 from the River Itchen, in Hampshire, and from Loch Shieldaig, in 

 Ross-shire (Mus. Jeffreys), from a depth of twenty fathoms. This 

 species is often attached to wood. At Ramsgate, the specimens were 

 attached to a small coasting vessel, and they must have been immersed 

 five or six feet ; they were associated with B. crenatus, and with a few 

 of B. balanoides. In the Brit. Mus. there are specimens collected by 

 Mr. Redman, from Nova Scotia, in North America. When her Majesty's 

 ship Beagle was beached at Santa Cruz, in Southern Patagonia, nume- 

 rous specimens were found adhering to her copper bottom, some so 

 small as to show that the species breeds in those latitudes. Near 

 Monte Video, in the estuary of La Plata, I found many large, but much 

 corroded specimens, adhering to some rocks in a small running stream 

 of perfectly fresh water. The rise of the tide is here small, but at 

 high water the specimens apparently were for a short time covered by 

 the waters of the estuary, here itself only brackish, and occasionally 

 almost fresh. I took home some specimens, and placing them in per- 

 fectly fresh water they continued for many hours expanding and 

 retracting their cirri witli perfect regularity and vigour. Here then we 



