180 SVEN LOVEN. ON TIIF, ECIHNOIDEA DESCRIBED BY LTNN.IOUS. 



Of tliis Linncau spccies no spccimcn luxs been left in tlie 

 coUection. From its abscncc in tlic list of Thunbekg it niay 

 be couclndcd tbat it litxd boen lo8t at Drottnino-holm durinir 

 tlie lifctimc of LiNN.EUS and perhaps even beforc 1754, and tliat 

 tliis is the causc ol' thc confnsion. Its limits werc altered 

 considcrably iu tlic coiirsc of time. In 1752 Linn.eus dictated : 

 »Ecliinus planus, lobatus, ambulacris (juinis ovalibus. Is called 

 the opercnlum. Gualtieki, t. 1 10, f. E, F, H. It is divided 

 inte sevcral lobes wliieli do not alwavs obscrve tlie like nnm- 

 ber and form ; lience the old antliors have split it into four 

 species.» It follows from the term »lobatns», thus explained, 

 and from the refercncc to Gualtieki, that Linn.eus originallj 

 liad in view tlie two West African species, which now con- 

 stitnte tlie genns liotula: the /:/ and y of the i\I. L. U., the 

 former being the l\. digitata Lamck., Gualtieri's //, H^), the 

 latter the R. dentata Låmck. He liad observed that during; 

 growtli their lobes increasc in number and take altered shapes, 

 and tlience was led to regard them as varieties of one and 

 the same species, into whicli he inclnded also the West Indian 

 ]Mellita pentapora Gm., in the iive »foramina» of which he 

 thonght he saw the beginning of a division into scparate lobes. 



In the M. L. U., published a long time afterwards, in 

 1764, this view is maintained witliout modification, and the 

 detailed diagnoses of the (i and the / even seem to indicatc 

 that LiNN.EUS had an eye to their distinctness as species. 

 Long before, however, in the S. X. ed. 10. 1758, he liad added 

 a fourth form: »rJ, foraminibns nullis pervins, indivisns», the 

 present Lagannm orbiciilare Gm., and for its sake liad strnck 

 ont the word »lobatns» of the diagnosis, and replaced it by 

 »suborbicnlatns». By this procedure the Echinns orbievdns L. 

 became a scollective species», and so it remained in the S. N. 

 ed. 12, 1767. Its name must be dropped, provided it may 

 not, — as has been done in many similar cases — be applied 

 to the one form alone, for which it was originally intended, 

 the a of the S. N. ed. 10, the Kotula dentata Lamck., and 

 the other Linnean varieties be pluced under their respective 

 species. 



') It is to be remerabercd that Gualtieri"s t. 110. f. /', F, is a 

 Rotula ditritata {If, H) in whicli the two anterior iforaniina» have bruken 

 through the margin so as to produce iocisions, and tliat, iu the drawing, 

 thc excretory opening has been misplaced. It is the Rotula Gualtierii of 

 Gkäy, Cat., p. 18,rightly trausferred by Al. Agassiz to the Uotula digitata. 



