3^ NOTES ON A COLLECTION OF CALIFORNIAN NUDIBRANCHS. 



The specimens are small and the majority are not well preserved. This 

 is especially regretable in the case of the two rather remarkable new genera 

 Dirona and Phijllohranchoijsis, but the characters which can be established 

 with certainty seem to warrant the descriptions here given. The small 

 size of the specimens, particularly the Dorids, is noticeable. It does 

 not appear to be charactistic of the Californian fauna for it is not supported 

 either by Mac Farland's observations or by my own made when visiting this 

 coast in 1899. Mr. Cockerell collected both at San Pedro and La Jolla in 

 July and August, It seems probable that the animals spawn early in the 

 summer so that at this period young and half-grown individuals are prevalent. 

 The specimens of Hermi^senda on the other hand are larger than those 

 recorded hitherto. 



The latitude of San Pedro and La Jolla is about the same as that of the 

 Canary Islands, and as far as the nudibranchs of this part of the Atlantic are 

 known, the character of the fauna in this group seems much the same in both 

 Oceans. The northern element appears to be the stronger, as shown by the 

 prevalence of forms like A?x'hidoris, Cadlina, AcantJiodoris, Aldisa, Rostanga 

 and various Polycerids, while such tropical genera as Chromodoris and Dorid- 

 opsix are sparingly represented. Plafydoris, so common in the Indo-Pacific, 

 has not yet been found in California, but Chromodoris appears to extend 

 further north than in the Atlantic, being recorded from Puget Sound. 

 Specially characteristic of this coast is the number of Polycerids, both in 

 species and individuals, such as Triopha and Laila. Aeolids are also 

 abundant. 



Another remarkable feature of the nudibranch fiiuna of the Pacific coast 

 of North America is the number of species closely resembling or even iden- 

 tical with those found in the northern Atlantic. Bergh considers that 

 Archidoris tuherculata, AcantJiodoris pilosa, Lamellidoris hilamellata, Den- 

 dronotus arhorescens as found in these waters are not specifically distinguish- 

 able from the Atlantic forms. Spurilla chromosoma is nearly related to 

 Sp. neapolitana, AeoUdia herculea to Ae. i^apillosa, Tritonia palmeri to T. 

 pleheia and T. lineata, Aegvres alhopundatus to Ae. p)undiluren<:, Adalaria 

 pacifica to A. proxima. It is noticeable also that the fauna of New Zealand 

 and the extreme south of the Pacific as far as it is known presents many 

 analogies to that of the northern Pacific and northern Atlantic. On the other 

 hand, some of the commonest Californian nudibranchs belong to genera which 

 have not been found elsewhere, such as Triopha, Laila, Hermissenda 



The nudibranchs of this coast were first noticed by Cooper and Stearns, 

 but the most important contributions to our knowledge of them, are con- 

 tained in Bergh's Nudibranchiate Gastropoda of the North Pacific (1879), 

 published in Dall's Scientific Results of the Exploration of Alaska, and Mac 

 Farland's Preliminary account of the Dorididae of Monterey Bay, California 

 (Proc. Biological Society of Washington, Feb. 2nd, 1905, vol. xviii.). It is 

 understood that the latter autlior is about to publish a fulUr account of the 



