AN UNDESCRIBED ACRANIATE. 233 



M.S." Samarang " and " as what appears to be a new species of 

 Lancelet," is described in a rather vague and unsatisfactory way 

 from a single specimen. Another was sent to Dr. Clarke, R. N., 

 for anatomical study, which appears never to have been made 

 public. 



Moreover the author compared this new form with specimens 

 from Cornwall and from the Mediterranean and concluded they 

 were all three different species. This opinion was maintained 

 again in the subsequent Catalogue of the British Museum (6) where 

 Gray calls the Naples form B. lubricum, that from Borneo B. 

 Belcheri and those from Polperro and S. W. England as well B. 

 lanceolatum. 



In the following year Sundewall (7) added to the knowledge of 

 the group by his description of the specimens in the Museum of 

 Stockholm. Amongst these he distinguished a new species A. 

 elongatus, sent by Capt. Warngren from Chinchaoarna, Peru, from 

 A. lanceolatus, from the German Ocean as well as from the coast 

 of Cornwall. He included Gray's Borneo species in the genus 

 Amphioxus, as A. Belcheri. 



Soon afterwards (8) he recast these descriptions and, for the first 

 time, introduced the counting of the myotomes, or the muscle- 

 segments, as a means of distinguishing species of Acraniata, counting 

 not only the entire number of segments but also the number anterior 

 to the atriopore, between that and the anus and posterior to the anus, 

 thus defining the relative positions of these important structures. 



Branchiostoma lanceolatum (as he now calls it) has 36 -\- 14 -{- 11 

 = 61 myotomes in specimens from Northern Europe. B. elon- 

 gatum, from Peru, 49 -j- 18 + 12 = 79, while a new form, B. 

 caribceum, found at St. Thomas, at Rio de Janeiro and at the 

 mouth of the Plata has 37 -f 14 -f 9 = 60. 



The four forms thus far described were not, however, regarded, 

 generally, as specifically distinct. Thus Guenther (9) in 1870 in 

 his catalogue of the specimens in the British Museum included all 

 known forms under the single species B. lanceolatum. 



However, in 1876 some new specimens were brought from 

 Moreton Bay, Peale Sound, Northeast Australia, by Captain 

 Schleinitz of S. H. S. Gazelle and described by Peters (11) as 

 generically different from all known forms. As far as could be 



