144 
number of specimens in all stages of development, however, has 
revealed the remarkable faet that the posterodorsal arms are 
entirely absent in this larva, a quite unique feature among 
Ophiurid larvæ, so far as hitherto known. It is curious that this 
interesting faet has escaped the observation of H. C. Chadwick, 
who in his Memoir on Echinoderm Larvæ l ) describes and care- 
fully figures the metamorphosis stage of this larva. His suggestion 
that it might prove to be the larva of Ophiopholis aculeata seems 
the more remarkable, since on the next page he mentions the 
larva referred by me (Echinodermenlarven d. Plankton-Exped. p. 53) 
to Ophiopholis aculeata , without giving any reason at all why 
that reference should be wrong. It is true, I could not then regard 
it as a definitely established faet that this larva really belongs to 
Ophiopholis aculeata , but it was pointed out that evidences are 
for the correctness of this reference. Having now myself (during 
a stay at the Biological Station at Trondhjem in July 1916) reared 
the larva of Ophiopholis aculeata to a stage corresponding to the 
youngest of the larvæ figured by Fewkes in his paper „On the 
development of the calcareous plates of Amphiura,“ 2 ) I have still 
less doubt that the reference of the said larva to Ophiopholis 
aculeata is correct, although the definite proof is still wanting, the 
reared larva having not yet developed the characteristic promin- 
ences of transverse rods. 
III. Brissopsis lyrifera (Forbes). 
Only four species of Spatangoids are known from the coast of 
Bohuslån, viz. Spatangus purpureus , Echinocardium cordatum , 
Ech. flavescens and Brissopsis lyrifera. The larvæ of the two 
former are known, more or less completely. 3 ) Chadwick in his 
*) L. M. B. Memoirs. XXII. 1914. Proc. & Transact. Liverpool Biol. Soc. 
Vol. XXVIII. 
2 ) Buil. Mus. Comp. Zool. XIII. No. 4. 1887. PI. I. 
8 ) Th. Mortensen. Echinodermenlarven d. Plankton-Expedition. p. 102. 
On the development of some British Echinoderms. 
Jour. Mar. Biol. Assoc. X. 1913. p. 14. 
E. W. Mac Bride. The development of Echinocardium cordatum. Part I. 
Quart. Journ. Mier. Sc. 59. 1914. 
