NUDIBRANCHIATA. 561 



coloured. The rhinophores are perfoliate and completely retractile. They usually emerge from 

 two of the anterior tubercles. Under the mantle edge are a large number of branchial 

 lamellae which form a more or less complete circuit interrupted only by the mouth and 

 genital oi-ifice and in Fryeria by the vent. The mouth parts consist of a minute poriform 

 aperture leading into a narrow tube, which passes into a large mass of glands that impart 

 a thick conical appearance to the anterior portion of the digestive tract (except in 

 Phyllidiopsis). Behind this glandular mass the pharynx reemerges as a thin tube, which 

 subsequently dilates and enters the liver. There is no exsertile proboscis as in Doridopsis. 

 The vent is usually dorsal and perforates one of the posterior tubercles. Only in Fryena 

 is it under the mantle rim. There are no jaws, radula or buccal armature of any kind. 

 The liver is not divided posteriorly. The verge is armed with rows of hooks. As in the 

 Doridopsidae the dorsal wall of the pericardium is furnished with a series of lamellae, and 

 the nervous system is much concentrated. A single blood-gland is present. 



The Phyllidiadae are Dorids in virtue of their unbranched liver, their two spermato- 

 thecas, their retractile rhinophores, and their usualty dorsal vent. The suctorial mouth, the 

 concentrated nervous system and the so-called pericardial gill ally them to the Doridopsidae, 

 but still the group Porostomata proposed for the two families by Bergh seems, as he himself 

 admits, somewhat artificial, for the absence of the ordinary branchial rosette and the position 

 of the branchial lamellae under the pallial margin separate the Phyllidiadae decisively fi-om 

 all Dorids except the Corambidae. From that family however they are equally decisively 

 separated by the structure of the mouth parts and the general habitus. 



The family is divided by Bergh into four genera, Phyllidia, Phyllidiella, Fryeria and 

 Phyllidiopsis. Fryeria is shaqily distinguished from the others, the vent not being dorsal 

 but terminal and under the mantle rim. Phyllidiopsis is also well characterized, as the 

 mouth parts resemble those of Doridopsis and the anterior part of the oral tube is not 

 surrounded by a large glandular mass as in the other genera. The distinction between 

 Phyllidia and Phyllidiella is less satisfactory. The former is said to have the dorsal 

 tubercles arranged in longitudinal rows and the latter in groups or quincunxes. But there 

 is much variety in respect of this arrangement. I have seen specimens of Phyllidiella nohilis 

 in which the tubercles appear to be arranged in rows, and the present collection contains 

 a specimen which has all the characters of Phyllidia varicosa, but in which there are only 

 seven tubercles scattered irregularly on the back and certainly not arranged in lines. In 

 dissecting a considerable number of specimens I have not been able to observe the difference 

 noted by Bergh in the mouth parts ; in Phyllidia forma tubi oralis glandula ptyalina obtecti 

 symmetrica and in Phyllidiella asymmetrica. The remarkable Phyllidiopsis papilligera^, which 

 has elongated papillae on the back, seems worthy to be the type of a new genus. 



The Phyllidiadae are abundant in the Red Sea, Indian Ocean, the Philippines and 

 Malay Archipelago, Polynesia and East Afiica. They are not recorded from the more northern 

 or southern parts of the Pacific, from the West Coast of America, North or South, from 

 the Mediterranean or Atlantic, except Phyllidiopsis papilligera from the Gulf of Mexico. 

 They seem therefore to be tropical forms and so little is known of the Nudibranchs of the 

 equatorial Atlantic that it is probable they will be found there. They appear to be mainly 

 littoral and inhabitants of coral reefs. Hardly anything is known of their manner of life, 



1 Bergh, Bull, of the Mus. of Comp. Zooloijij of Harvard posed the genus Ceratophyllidia to include this form and 

 College, six. 3. 1890. Since writing the above, I have pro- another which I have discovered in East Africa. 



G. II. 72 



