254 HERJLEID.E. 



Found by Mr. Alexander Agassiz at Naushon Island, September 

 1863. 



This is the only specimen of the genus yet found in American 

 waters. The description is drawn from an enlarged sketch of the 

 inferior face by Mr. Agassiz, no dimensions or colors being given. 

 Indeed, the tentacles are so imperfectly given as to render its place 

 in this genus a little doul)tfal. Its peculiarities leave no doubt as 

 to its being hitherto undescribed. Tlie l)ranchial organs are slender 

 at their hiscrtion and curiously dilated at the middle, as Avell as the 

 internal dark biliary contents representing a quaquaversal cross. 

 These are supplied by two lateral longitudinal vessels instead of by 

 a shigle dorsal one, as in most other Nudibranchs. 



Genus AL,I>ERIA, Alljian. 1844. 



Body ovate-oblong, without a cloak. Head terminal, distinct, 

 produced on either side into a lateral lobe. Tentacles none. Max- 

 illa3 none. Branchiae papillose, along each side of the back. Anus 

 posterior, on the median line of the back. Genital orifice anterior, 

 on the right side. 



Alderia Harvardiensis. 



Plate XVI. Figs. 226-228. 



Animal broad lanceolate, ochreous brown; foot yellow; lateral prolongations of 

 head tentacular ; branchte short, curved, enlarging toAvards tip, in about six clus- 

 ters of two each, on either side, of which the lower one is much smaller. 



CanthojKts Ilarvnrdioisist, Agassiz, Proc. Post. Soc. Nat. Hist. iii. 191 (1850), no de- 

 scription. — Stimpson, Mar. Invert. Gr. Manan, 25 (1853). 



Animal small, about three times as long as broad, square in front, 

 broad lanceolate behind, and somewhat acuminated at point, a lit- 

 tle contracted at sides. Color of body ochreous brown, of the foot 

 ochreous yellow. The body is square or a little concave in front, 

 the lateral extensions of the head triangular, but capable of consid- 

 erable extension so as to resemble short tentacles ; a little contracted 

 behind the head, and back a little excavated, but sides generally 

 parallel, abruptly narrowing behind and terminating by a nipple-like 

 vent. Branchiae short, slender at origin, enlargiug and quite blunt 

 at tips, somewhat curved, arranged two and two along each side, 

 beginning at some distance from head, in six or seven clusters, the 



