HANCOCK AND EMBLETON ON THE ANATOMY OF DORIS. 119 



We have here strong apparatus for the rapid lateral motion of 

 all the large fins, and for drawing forward and spreading the rays 

 of the dorsal and anal fins, and further, for the vertical, as well as 

 horizontal, motion of the head and spine. 



The bones generally are light, spongy and soft. Some of the 

 cranial bones, and the bodies of the vertebra), are the hardest. 

 There are eighteen or nineteen spinal vertebrae, of which several 

 caudal ones are cartilaginous. The first five behind the skull 

 have their neural spines very short, inclined backwards, and im- 

 bricated upon each other, but this part of the spine is very flex- 

 ible in all directions. Nearly all the other vertebrae have their 

 neural spines very long and straight. At the tenth vertebrjB the 

 hcemal spines commence, and are at once of full size. There are 

 no transverse processes. The interspinous bones are long, particu- 

 larly the hoemal, flattened and featherlike at their proximal, 

 narrow towards their distal ends, which present a small head for 

 articulation with the fin rays. 



The great apparent size of the head is owing almost entirely 

 to the unusual developement of the bones of the hyoid apparatus, 

 the opercular pieces, and the scapula. The branchiostegal rays 

 are five in number, long and attenuated. The maxillary and 

 praemaxillary bones are anchylosed. 



Circumstances have occurred which have prevented a more 

 detailed description of the bones of the cranium. 



V. — Summary of Observations on the Anatomy of Doris, a Nudi- 

 hranchiate Mollush. By Albany Hancock, Esq., and Dennis 

 Embleton, Esq., M.D. 



[Read, August 16th, 1850.] 



We have proposed to ourselves to communicate to the Club the 

 principal points of the Anatomy of Doris. The following species 

 have been examined, and are referred to: — D. tuberculata, D. 

 tuherculata, Verany, J). Johnst07ii, J), tomentosa, D. repanda, D. 



