TRANSACTIONS OF SECTION D. 685 



medium and ulnare, and largely so; in the riglit carpus an ossification occurs 

 also in the disto-carpal, of medium size. The radiale is not ossified in either carpus. 

 In the 35-feet-long male Mysticetus, in the right carpus (the left not obtained), tliree 

 ossifications occur, but they are in the radiale, the intermedium, and disto-carpal, 

 not in the ulnare. Moreover, in this two-thirds-grown Mysticetus the metacarpal 

 of the pollex is fully ossified, while in the adult the pollex is entirely cartila- 

 ginous. 



In the flnners, in the distal row, two cartilage bones, more or less ossified, occur 

 normally, supporting the two greatest digits. In the G.5^-feet-long B. musculus 

 these two are united into one bone, notches above and below and a groove on the 

 surface indicating synostosis of two formerly separate bones. In tbree of the five 

 B. muscuhis a disto-carpal was found supporting the inner of the four digits, car- 

 tilaginous in the 60-feet-long one and in the 60i-feet-long one, and with a small 

 ossification in the GoA-feet-long one. In the 45-f'eet-long one there was no trace 

 of this third disto-carpal, either bony or cartilaginous, nor was it present in the yC- 

 feet-long B. borealis, nor in either of the two adolescent B. rostrata. 



In the Meyfiptera, 40 feet long, the ulnare is a very broad bone, extending for 

 over one-third of its breadth below the radius, thus occupying also the locality of 

 an intermedium, and between it and the radiale occurs au undersized intermediate 

 bone. These two latter form the entire carpu«, as one row, between the radius and 

 the massive radial metacarpal. Small ossifications occur in the radiale and in the 

 ulnare to its ulnar side. 



The phifor7n is, in the great finners, large and square-shaped ; in B. rostrata, 

 narrow and directed npwards; in Mysticetus, transversely elongated. Rewarded 

 by some as merely a sesamoid, it serves as a stretcher, giving breadth to this broad 

 part of the limb, steadied by the flexor carpi ulnaris muscle, which the author has 

 found to be present in all the cetacea he has dissected, whether whalebone or 

 toothed. In the 60^-feet-long B. miisrulus it had an ossification as large as a 

 ■walnut. The pisiform may be said to be the only one of these bones adapted to 

 serve a function. The mass of cartilage forming the carpus serves to give some 

 low flexibility and elasticity at that part of the limb, like a piece of firm india- 

 rubber in the middle of an oar ; but the mapping into distinct cartilage bones, more 

 or less ossified, in these whales can be explnined only on the view of inheritance 

 from some mammal whose diarthrodially jointed carpal bones were adapted to allow 

 of particular movements. 



3. On the Sjjecies of Amphioxus. By J. W. Kirkaldy. 

 I. Branchiostoma Lanceolatum (Costa). 



Distribution. — Mediterranean Sea, English Channel, North Sea, Coast of 

 Norway. 



Gonads 26 pairs. 



Both metapleural folds die away hehind the atriopore. 



Myotomes ;^5, 14, 12. 



Snout fin of medium size, pointed. 



Caudal fin lancet-shaped. 



II. Branchiostoma Californiense (Cooper). 



Distribution. — Coast of California. 



Gonads 31 pairs. 



Both metapleural folds die out behind the atriopore. 



Myotomes 45, 17, 9. 



Head region very small, snout fin not marked oft" from the dorsal tin. 



Tail fin long and shallow. 



III. Branchiostoma Belcheri (Gray). 



Distribution. — Borneo and Torres Straits, Australia. 



Gonads 25 pairs. 



Both metapleural folds die out behind the atriopore. 



