:;o NOTES ON A COLLECTION OK CALIFORNIAN NUDIBRANCHS. 



consists of many white follicles; the mucous and albumen glands large; the 

 spermatotheca strong and rather elongate. The central nervous system is 

 very strongly granulate; the cerebro-pleural ganglia are elongate, the pleural 

 rounder. 



Hermisenda opaleseens (Cooper). 



Bergh : Explor. of Alaska, Nudibr. I, p. 138. 



Cockerell is probably correct in referring to this species, a numl)er of 

 specimens found at San Pedro and in regarding it as identical with the 

 Eolis dpa/«'f<'-niK of Cooper from Sun Diego, although Bergh 's specimens 

 from Alaska were much smaller and there were soine discrepancies in 

 colour. 



This nudibranch was found abundantly on mud flats at low tide in San 

 Pedro harbour on July 19, 1901, and attained a length of 42 millims. The 

 papillae were arranged in thick groups and were deciduous The tentacles 

 and sole of the foot were of a beautiful opalescent blue and a stripe of the 

 same colour ran down the middle of the biick, bifurcating anteriorly so as 

 to enclose an oblong area of bright orange. In some individuals there was 

 a similar orange area in the middle of the back. Some pink internal organ 

 could be seen through the integuments, and there was a broad orange stripe 

 on each side of the head passing backwards from the oral tentacles. The 

 cerata were yellowish with bluish tips, and the hepatic diverticula varied in 

 colour from purplish to very pale brown, the lighter colour being the com- 

 moner (figs. 17, 18, 19). 



The preserved specimens are of a uniform pinkish or violet grey ; the 

 length varies from 15 to 20 millim., the breadth across the cerata at the 

 widest part from 7 to 9. The external and internal characters seem to agree 

 with Bergh's description, allowing for the difference of size. 



The cerata are set in four or five thick groups, of which the first and 

 second are somewhat raised, the others less distinctly so. The innermost 

 cerata are largest, the outermost very small. The foot is broad, thickened 

 and grooved in front, and produced into grooved tentacular angles. The 

 tail is long and thin, extending 5 millim. behind the cerata in large speci- 

 mens. The rhinophores bear about 20 distinct perfoliations. In several 

 specimens the oral tentacles simulate perfoliation in a remarkable manner, 

 but the ])henomenon is apparently due to contraction as in other specimens 

 they are smooth and simple. 



The jaws are yellowish and bear a line of pointed denticles which are 

 themselves serrulate in the hinder part. The radula consists of aliout 25 

 yellowish teeth with 4 — 6 longish, curved denticles on each side of the 

 central cusp. 'I'hese denticles are sometimes irregularly shaped or bifid. 

 The under side of the central cusp is irregularly serrulate, the serrulations, 

 though not always easy to see, amounting to at least ten. Bergh mentions 

 that a layer of rather short sacculate glands filled the end of the j)enis 



