191 
has completely disappeared. The auricles were found to be com- 
pletely absorbed in the specimen of 1 1 mm. 
The discovery of the young Echinobrissus having a well developed 
dental apparatus which disappears completely long before the animal 
has reached its full size, is a most interesting parallel to Wester- 
grens discovery of a dental apparatus in the young Echinoneus, * 1 ) 
and leads to the suggestion that a dental apparatus will be found 
to exist also in the young of Echinolampas and upon the whole in 
the Cassidulids. 
It is a surprising faet that the lantern of Echinoneus and of Echino- 
brissus have proved to be of very different structure. (In Echinoneus 
the compass is typically developed, bi fid, radial compass muscles 
being present. The lantern is erect and perfeetly regular. The whole 
apparatus has disappeared already in specimens, 5 mm long). As 
pointed out by Jackson („Phylogeny of the Echini“, p. 189) the 
lantern of Echinoneus recalls to a striking degree that of Arbacia, 
and, upon the whole, of the Stirodonta, which would tend to show 
that the Echinoneids are derived from that group of the regular 
Echinoids. The imperforate character of the tubercles is in good 
accordance herewith. The dental apparatus of Echinob rissus, on the 
other hånd, is of a markedly different character, showing no relation 
to the Stirodonta; it recalls the Clypeastroid lantern in its main 
features, especially it has a surprising likeness to the lantern of Echin- 
ocyamus. The Clypeastroid affinity of Echinobrissus is also expressed 
oy the peculiarity that it turns green on preservation in aleohol, or on 
3eing damaged, a property so highly characteristic of the Clypeastroids. 
I am not aware, whether Echinoneus has the same property). Further 
he larva shows Clypeastroid affinities. 2 ) It would thus seem evident 
hat Echinobrissus, and, consequen tly, the Cassidulids 
jpon the whole, are not nearly related to the Echino- 
ieids, but that these two groups are of entirely dif- 
r A. Agassiz. On the existence of teeth and of a lantern in the genus 
Echinoneus. Amer. Journ. Sc. 4. Ser. vol. 28. 1909 p. 490—92. PI. 2. 
A. M. Westergren. Echinoneus and Micropetalon, Rep. Sci. Res. 
Exped. to the Tropical Pacific, U. S. Fish. Comm. Steamer „AlbatrossT 
i 1899—1900. XV. Echini. Mern. Mus. Comp. Zool XXXIX. 1911. 
Th. Mortensen. Studies of the development and larval forms of Echino 
derms. 1921. p. 118. 
