178 T. GisLÉN, 



of the 11 and III Br-series in the two species. The number of II 

 Br — s, however, in M. rotundus is somewhat more variable (2 — 7 — 11 

 — 21) than in M. interriqdii.s, where, with rare exceptions, it stops bet- 

 ween 9 and 11. Further I quite agree with Sperrt in his statement 

 about the variability of the infranodal face. 



But — nevertheless — there are some differences. In the <jri- 

 ginal specimens of M. rotundus and interruptus there was measured 

 a stem-diameter of o,o and 4,25 mm. respectively. This difference 

 might seem slight, but my measurements of both the species show that 

 it is of rather great importance: only 4 of the 22 specimens of M. 

 interruptus have a stem-diameter of more than 4,2 mm., and these 4, 

 evidently very old specimens, do not attain a stem-thickness of more 

 than 5,1 mm. In M. rotundus, on the other hand, there are only 2 

 specimens (with relatively rapid growth of the stem) which do not come 

 up to 6 mm. (Carpenter's specimen is evidently to be compared with 

 the Bockian Sp. 5); all the full-grown ones have a diameter of the 

 stem of 6,0 — 6,7 ram. 



M. rotundus is therefore a larger species and from this some other 

 differences also follow. Thus the cirrals often number 50 — 55, cont- 

 rary to M. intemiptus, where they veiy seldom exceed 45. The inter- 

 articalur pores in the latter species disappear at the 7* or the 8'''^ in- 

 ternodes (seldom at the 9*'' or 10*''), in the former species they dis- 

 appear first at the 9"' — 12"' internodes. 



As to the number of the ossicles in the I Br-series a compa- 

 rison between the two species turns out thus: M. rotundus has 7 I Br-s 

 in 26 cases, 8 or 5 each in 4 cases; 4, 10 or 12 each in 1 case. (It 

 is, however, to be noticed that here are included the figures from the 

 abnormal Sp. 7). M. interruptus has 7 I Br-s in 76 cases, 8 in 5 cases, 

 5 and 6 each in 2 cases, 4 and 9 each in 1 case. (Here the young 

 specimen 16, however, contributes 3 figures differing from 7). Thus 

 it is impossible to deny that in M. rotundus there is a somewhat greater 

 variability in the number of the I Br — s. 



The cirri extend over 2'/2 — S'/s internodes in 3I.rotundus, over 

 I'/a — 2^/3 internodes, only exceptionally over 3 internodes, in M. inter- 

 ruptus (Sp. 11, 21). (The last-mentioned L only occurs in the largest 

 specimens). 



