406 Dr. J. E. Gray on the Affinities of Camptonyx. 



The genus Cystingea with its terminal cloacal opening, so far 

 as the disposition of its ahmentary canal is concerned, agrees 

 rather with the characters given in the left-hand column ; but 

 in nearly all other particulars, as may be gathered from Mr. W. 

 S. Macleay^s beautiful description, its affinity to Bultenia can 

 scarcely be questioned. 



EXPLANATION OF PLATE XL 



Fig. I. Chondrostachys, natural size. 



Fig. 2. One of the zooiils, with a portion of the axis magnified : a, bran- 

 chial, and b, cloacal orifice ; c, branchial network ; d, endostyle ; 

 e, pseudo eye-speck ; f, mouth ; g, oesophagus ; h, stomach ; 

 i, intestinal loop ; A:, rectum ; I, heart ; m, ovarium ; n, ova 

 occupying a sacculus of the duct (two others are seen in the 

 branchial chamber) ; o, testis ; ji, vas deferens ; q, pallio-vascular 

 process leading into the stem. 



Fig. 3. Transverse section of stem. 



Fig. 4. Longitudinal section of the same, on a larger scale. 



Fig. 5. Csccal end of one of the tubules, more highly magnified. 



Fig. 6. Ventral surface of a zooid removed and laid out to show the rela- 

 tion of the pseudo eye-specks a ff to the ganglion b ; c, branchial, 

 and d, cloacal aperture ; e, some of the oral tentacula protruding 

 inferiorly. 



Fig. 7- Tadpole-like embryo within the ovum (one of the three suckers, 

 being situated upon the dorsal aspect, does not present itself in 

 this view) : a, otolithic sacs. 



Fig. 8. Enlarged figure of the otolithic sacs lying upon the ganglion : 

 a, otolithes separated from the investing pigment-granules. 



XXXVII. — On the Affinities of the genus Camptonyx, Benson. 

 By Dr. Gray, F.R.S. &c. 



There can be little doubt that this genus is a new form of 

 amphibious mollusk, characterized by its cap-like shell, with a 

 groove and keel on the side ; but I think, from the account of 

 the position of the eyes, the shape of the tentacles, and the form 

 of the muzzle, as well as the peculiar colour of the shell, that it 

 is much more nearly allied to Otina than to Ancylus, with which 

 Mr. Benson compares it. 



Otina is nearly as terrestrial ; it lives among Lichina on rocks 

 near the sea, sometimes within reacli of the spray, and more 

 rarely in parts covered by the water at very high tides ; but it 

 is essentially terrestrial; and as many plants are common to 

 the sea-shore and mountains, the difference between the habitat 

 of Otina and Camptonyx is not very great. 



tween Clavelina and Syntethys. The relation of the intestine to the bran- 

 chial sac in Chondrostachys removes it from that group of Ascidiaus to 

 which Boltenia belongs. — Ed.] 



