190 
ever this that there is a well developed dental apparatus in the yonng 
specimens. The lantern (PI. VIII, Figs. 1-2) is conspicuously un- 
equally developed, the anterior part being the smaller, the postenor 
part the larger, It is much inclined in the lower part, the .mer- 
pyramidal muscles being large, while in the upper part it ,s qu.te 
vertical. The surface for the attachment of the interpyramidal muscle 
is smooth not striated. The foramen magnum is fairly deep. not 
bridged over by the epiphyses. Styloid processes not visible from 
the outside. The epiphysis is a small, compressed plate, fit into 
a slight impression on the upper part of the pyram.d; it .s of a 
peculiar shape, high in the outer part, the inner part low, formtng 
l ike a small handle (PI,VIII, Figs. 3-4). No pits m the pyramtd 
on the attachment face for the epiphysis. The brace is reduced to 
a very small plate (PI. VIII, Figs. 1, 3b) lying at the inner, adoral 
end of the furrow between each two adjoining pyramids. Th,s 
furrow shows three narrow, parallel, rounded ridges; the twt> outer 
ridges are the epiphyses, the median the compass (PI. VIII, Fig. 1). 
Thfs is divided in two. sometimes three pieces. They differ con¬ 
spicuously in shape from that typical of the compass, being high, 
compressed, with the upper edge somewhat thickened, not t in, 
cylindrical as usual. This is in correspondance with the faet that 
,hey are fastened between the epiphyses, not lying free above the 
pyramids as does usually the compass. The teeth are keeled, t e 
pulpa small. The protractor muscle is fastened to the first mter- 
ambulacral plate, the retractor muscle to the ambulacral auncu es, 
which are simple, rounded prominences. The intercompass muscle 
is very slightly developed and seen only with difficulty; but in good 
light it may be seen distinetly and there is no doubt of its existence. 
Radial compass muscles, on the other hånd, are absent. 
It is quite evident that the dental apparatus is larger in a specimen 
of 7 mm than in one of 5 mm in length, so that accordingly a growt 
has taken place along with the inereasing size of the ammal. e 
more remarkable is the sudden change which then occurs, t e w oe 
apparatus being completely absorbed in the course of rather short 
time. In a specimen, 9 mm in length, only some half absorbed rests 
of the pyramids are found lying round the mouth (PI. VIII, Fig. 5 . 
In a specimen, 1 1 mm long, some traces of the lantern are st. 
discernible; in specimens beyond that size the whole dental apparatus 
