ACTINLZE FROM THE MERGUI ARCHIPELAGO. 253 



evident that Hertwig should have referred his species to the 

 former rather than to the latter of the two genera. In which 

 case the following would constitute the recognized species of the 

 genus HormatMa, viz. H. Margarita, Gosse, H. pectinata (R. 

 Hert.), R. Andersoni, Hadd. I shall shortly in another place 

 discuss the systematic relationships of this genus. 



Of the three specimens collected by Dr. Anderson, one (a), 

 PI. XX. fig. 1, is attached to a piece of broken shell, the base being 

 greatly expanded and partially enwrapping the fragment of shell. 

 In the other two specimens (b and c), PI. XX. figs. 2 & 3, the base 

 is dome-shaped and constricted off from the upper portion of the 

 column ; possibly these were free forms, as the arrangement of the 

 base would form an efficient sand- anchor. 



As was previously mentioned, one specimen was sacrificed for 

 anatomical purposes. First, I bisected it vertically, and then 

 devoted one half to transverse sections ; a portion of the other 

 was utilized for vertical sections. This specimen was in a good 

 state of preservation. 



Professor Hertwig has in his 1 Challenger ' Eeport, pp. 80-83, 

 given a good account of the genus HormatMa, as represented by 

 his P. pectinata. Our form is so closely allied to this, that little 

 need here be added. Fig. 3 (PI. XX.) is a slightly diagrammatized 

 view of a vertical section through the entire animal. The 

 powerful mesodermal circular muscle, the folded oesophagus, 

 and absence of gonidial grooves alone call for remark. The ecto- 

 derm is figured as extending entirely round the body ; as a matter 

 of fact in the specimen in question it only occurred in the more 

 protected portions, as, for instance, in the slight hollow round 

 the central boss, at the basal constriction on the pedal disk, and 

 on all the invaginated surfaces. 



Two figures of transverse sections are given : one (Pl.XX. fig. 4) 

 is taken through the circular muscle, and shows that the sphincter 

 forms an uninterrupted circular muscle, the apparent terminations 

 in the section being due to the section passing out of the plane 

 of the muscle ; the second section passes through the oesophagus, 

 and illustrates a characteristic feature of the Chondractininse, that 

 only the primary pairs of mesenteries reach the oesophagus. This 

 section is slightly oblique, the left-hand side being at a somewhat 

 lower level than the right. At the latter the tips of three 

 tentacles are cut across. 

 The mesenteries have no features worthy of special note. 



