29 



dorsal rod ) may be double (Fig. 3 A). The postoral rods are fenestrated, 

 thorny. 



In a plankton sample from off the island of Taboga from the end of 

 November 1915 three specimens of an Echinopluteus were found, which 

 may with no small degree of probability be referred to Aslropyya pulvi- 

 nala. (PI. V, Fig. 7). The larva shows so considerable resemblance to that 

 figured by Joh. M tiller in his VII. Memoir on the Echinoderm larvae 

 (Taf. V) that it seems beyond doubt they must be nearly related to one 

 another. Joh. Mtiller referred his larva to Centroslephanus lonyispinus. 

 There is still no definite proof that he was right herein, but there is nothing 

 either to disprove the correctness of this reference. The present larva 

 should then also be referred to a Diadematid. Diadema me.ricanum being 

 out of question as not having its breeding season at this time of the year, 

 Aslropyya pulvinala, the only other Diadematid known to occur here, 

 should then be the species to which this larva belongs. (A new Aslropyya 

 found by the author at Las Perlas - - not yet described - - hardly comes 

 into consideration). It should, however, be pointed out that the postoral 

 and posterodorsal rods are entirely smooth in these larva. 1 , while in the 

 reared young larva 1 of Asfropyya the postoral rods were found to be 

 distinctly thorny. This fact is thus not in favour of the supposition 

 that these larvae belong to Aslropyya. Since, however, they must in all 

 probability belong to a form which has a near relative in the Mediterra- 

 nean, there is hardly any other Echinoid which could come into regard - 

 be if not Eucidaris Thointrsi, which I would not think very probable, 

 judging from the shape of the young larva reared. 



The extensive development of the vibratile lobes, Ihe very long posloral 

 and posterodorsal arms ( - they are broken, so thai their full length 

 cannot be ascertained, but they are very long ---), and otherwise the 

 whole shape of the larva is very much like that of the Mediterranean larva. 

 Kchinopluleiis Mullen, as I have named it. The posterior transverse rod 

 has a long median process to each side. 



Arbacia stellata (Blv.) 1 ). 



PI. vn, i-'i. :;. 



Although a considerable number of young specimens of this species 

 was secured at Taboga, Panama, only a single adull specimen was observed, 



') II. I., ('.lark in his paper Kchinoderms from Lower California, with 1 >escriptions <d 

 new Species" ( Hull. Amer. Mils. Nat. Hist. XXXII. KM.'!, p. ITJiM rejects Ihe name Arbnciii 

 stcllald (Blv. I. because of Ihe name AY/ii/ii/-.- xli-llattix being used by Ciiiu-lin (I.inn. Sysl. 

 Nat lira. 1 . Bd. XIII. 17SS. p. :!171). -even though \\ e do not know at present what species 

 Gmelin had in mind": instead of Ihe long used name A.xli'llitln (Blv.) he then names it 

 Arbacia incisa (A. Ag.l reviving Ihe name given to this species by Agassi/ in ISti.S. I do 

 not see the necessity of making this change, anil therefore keep the old name. 



