74 first Annual Report 
Thais ostrina Gld. 
While dead shells are fairly common between tides, living speci- 
mens appear to be rare here. 
Astyris hindsii Roe 
Fairly common on sea-weeds between tides. 
Amphissa versicolor Dall. 
Empty shells of this only, were encountered. 
Macron lividus A. Ads. 
Common attached to fucus. 
Volvarina varia Sby. 
Between tides, but not common. 
Olivella pedroana Conr. 
A few dead shells found. 
Conus californicus Con. 
Common, attached to fucus. 
OPISTHOBRANCHIATA 
TECTIBRANCHIATA 
Aplysia californica Cooper 
(Figure 37) 
These enormous purplish sea-slugs were occasionally encountered 
in the lower tide-pools. A good many specimens were dissected. 
NUDIBRANCHIATA 
Numerous species of remarkably beautiful nudibranchiate mol- 
lusks are to be found at Laguna Beach, and they are among the most 
attractive objects of the tide-pools, never failing to call forth the 
most enthusiastic exclamations from both students and visitors. 
‘‘Hixquisite’’ is the only word that adequately described them. I 
determined the species so far as | could from MacFarland’s writings, 
but a large part of the species seem to be underscribed. In the works 
of Bergh and other writers on this group, our west coast species 
seem never to have been treated. 
Chromodoris porterae Cockerell 
(Figure 39 B) 
Color prussian blue, the dorsum of a deeper shade than the sides. 
Mantle narrowly white edged. On the dorsum is a median line of 
light blue running from between the rhinophores to the branchie. 
On each side, half way between this line and the mantle edge, a broad 
