28 MADEEPOEAEIA. 



surface, dense and finely echinulate, and the wall finely striate. This condition may perhaps 

 be due to secondary deposition of lime. 



In the description of this and the preceding variety I have endeavoured to give the leading 

 characters of comparatively typical specimens ; but it must be understood that numerous 

 intermediate forms occur which it would be difficult to allocate satisfactorily. The forms 

 described by Ehrenberg as M. laxa and M. regalis appear to correspond roughly with M. pro- 

 Ufera and M. cervicornis, Lamk., though in some respects both show intermediate characters. 

 Klunzinger instituted the name M. superba for the former, and pointed out that, although 

 Ehrenberg^s type is recorded as from the Red Sea, the specimen had attached to it a specimen 

 of Trochus imbricatus, Gmel., which is a West- Indian shell, and that therefore the recorded 

 habitat is probably not correct. A specimen in the Berlin Museum, from Hayti, agrees very 

 closely with the type specimen of M. regalis. After a careful comparison of the types of 

 Lamarck and Ehrenberg with the fine series of West-Indian and other specimens in the 

 British Museum, I have been unable to recognize any constant characters by which the 

 species may be distinguished from one another. It has therefore seemed advisable to rega'rd 

 all as variations of one species, common to the Atlantic and Indo-Pacific Oceans. Pourtales 

 has pointed out, with regard to the West-Indian specimens of palmata, cervicornis, and 

 prolifera, that the proper habit and robustness of each form is associated with a difBerent 

 position on the reef. M. palmata grows in situations exposed to the force of the sea ; 

 M. cervicornis in less exposed localities ; whilst, for its full development, M. prolifera appears 

 to require sheltered spots on the inner side of the reef. The form M. palmata, Lamk. 

 (including the various synonyms), is usually readily distinguished from all the others by its 

 habit. Of the arborescent varieties, M. prolifera, Lamk., M. superba, Klz., M. regalis, Ehrb., 

 and M. cervicornis, Lamk., form a consecutive series in which the habit gradually becomes 

 more erect, the branches stouter, and the corallites relatively shorter. 



The specimens hitherto recorded under the various names included in the synonymy, 

 beginnifig with Lamarck, nearly all come from the West Indies. The doubtful origin of 

 Ehrenberg's specimens has already been alluded to. Dana^s type of M. alces is queried 

 from the East Indies, as was also the specimen figured by Rumphius to which he refers. 

 Briiggemann's Rodriguez specimens do not appear to me referable to that species ; and the 

 specimen recorded by Ortmann from Panama does not differ materially from alciform 

 specimens of M. palmata from the West Indies ; added to which Dr. Ortmann informs me 

 that the habitat is not certain. On the other hand, Mobius has recorded the form 

 M. superba, Klz., from Mauritius, and Paurot has recently obtained the same variety from 

 the Gulf of Aden. Some of the specimens from Singapore, referred by Ortmann to 

 M. secunda, Dana, appear to me to agree closely with West-Indian specimens of M. cervi- 

 cornis, Lmk., and, indeed, are the only specimens I have seen from the Indo- Pacific Ocean 

 in other collections which do so. The most frequent Indo-Pacific variety appears to be 

 M. superba, Klz., or M. regalis, Ehrb. ; but a shallow vasiform specimen of M. palmata is in 

 the collection of the British Museum. Several specimens of this species were collected by 

 Mr. Saville-Kent at Thursday Island &c. One specimen is almost identical with a West- 

 Indian specimen of M. cervirornis in the British Museum, and a plate-like form with confluent 

 branches also occurs there. Thus the three chief varieties of the species occur both in the 

 Atlantic and Indo-Pacific Oceans ; but apparently they are nowhere so abundant as in the 

 West Indies. 



West Indies and Indo-Pacific Ocean (Red Sea to Tahiti). 



