MR. J. D. MACDONALD ON THE ANATOMY OF EURYBIA GAUDICHAUDI. 249 
EXPLANATION OF THE PLATE. 
Tas. XLIII. 
Eurybia Gaudichaudi. Natural size. 
. Eurybia Gaudichaudi, magnified to show more distinctly its head, tentacula, oral aperture armed 
with lateral dental cells, the swimming-fins, and foot. The abdominal viscera are imperfectly 
seen through the transparent mantle. 
Portion of the fibro-cartilaginous mantle, highly magnified. 
The lateral labial teeth, forming in this case a double series. 
Six of the dental cells belonging to the right side, still further magnified to show the longitudinal 
cutting edge near the external border of each. 
- Three transverse rows of the lingual ribbon. In this view the curvature of the lateral teeth is 
scarcely apparent. 
The auditory capsule containing otokonial particles. 
Generative systems: A a. expansion of the lobules of testis and ovarium lying in juxtaposition ; 
A b. ova seen through the walls of the ovarian lobuli; A c. primary oviducts uniting in A d, 
the common duct; A e. vesicula seminalis; A f. the vas deferens; B a. pointed extremity of 
the penis, composed of indurated cells, and traversed by the ejaculatory canal; m à. sperma- 
tozoa exhibiting their peculiar looping and twisting movements. 
. Embryo of Eurybia within the ovum: a. frontal and lateral ciliated head-lobes; 5, 6. subæso- 
phageal ganglia supporting the auditory sacs with their single primordial otolithes ; c. alimentary 
canal with the rudimentary abdominal viscera; d d, d d. two ciliated rings which gird the exte- 
rior of the incipient cartilaginous mantle. 
Fig. 10. Structural elements of the mantle: a. portion of one of the ciliated rings of the embryo; 
b. stages of development of the fibrous tissue ; c. cartilage-cells in different stages. 
