NUDIBRANCHIATA. 549 



Gen. Trevelyana Kelaart*. 



The shape of Trevelyana is limacifonn, there being no mantle margin or distinction 

 between the back and sides and no appendages. The rhinophores are retractile and perfoliate. 

 The branchiae, which are generally placed about the middle of the back, vary in number 

 (7 — 32), but are usually numerous, simply pinnate or compound. The tentacles are small. 

 There is no labial armature or rhachidian tooth. The radula is short and narrow : the first 

 and sometimes also the second tooth differs in shape from the others. There are two or three 

 distinct hermaphrodite glands not attached to the liver. The verge is armed. 



Trevelyana is only recorded fi-om the Indo-Pacific area, but within it is one of the 

 commonest of polycerids, and is frequent under stones in the littoral zone, e.g. in East Africa. 

 It is generally found in pairs. 



6. Tr. crocea B. 



Two specimens from Hulule. Length 24 cm. : breadth 1'2. Body rather square and 

 stout : well preserved, but the colour lost, the whole animal being of a uniform greyish-white. 

 Rhinophores small, with about 12 perfoliations, and retractile into simple pits without raised 

 margin. Branchiae 20 in both individuals, forming a circle open behind, which is completed 

 by the anal papilla. The gills are bent inwards, and on their inner side are simple lamellae. 

 The tentacles very small: the radula is composed of about 15 rows: the two teeth next to 

 the rhachis are bicuspid, consisting of a basal portion, from which two hooks arise : the others 

 have a single hook, which is much reduced in the outermost. The nervous system is rather 

 large, and shows the various ganglia very distinctly divided. There are two distinct herma- 

 phrodite glands close together, and not spread over the liver. The verge is armed with small 

 spines. Prostate large. 



Though there is no record of the colour of the living animal the specimens seem 

 referable to Trevelyana crocea on account of the number of the branchiae and the shape of the 

 teeth. 



Gen. Nemhrotha Bergh-. 



Externally this genus closely resembles Trevelyana, and differs only in the gills, which 

 instead of being numerous and small are few in number, but very stout and strong. Internally 

 it differs in the structure of the radula and generative organs. There is a squarish central 

 tooth, with a large hamate latei-al at the side. The remaining teeth, which vary in number 

 from 3 to 12, are also generally squarish plates without hooks. The hermaphrodite gland 

 is spread over the liver, and not separated into distinct masses. There is no prostate. As 

 a rule there is no labial armature, but a weak one exists in N. nigerrima. 



7. Nemhrotha nigerrima ? variety. 



One specimen from Minikoi, much bent and contracted. Length 3'4 cm., breadth 1-6, 

 height 2'4. Colour, a uniform dirty yellow : the gills and rhinophores are much redder, and 

 there are a few raised reddish spots, particularly near the gills. The rhinophores small, with 

 about 30 perfoliations : the skin round the rhinophore openings is much contracted, but no 

 raised edges were discernible. The gills large, 5 : two on each side and one in front. As 

 in other species of JVembrotha which I have seen the rhachis is very hard and strong, so 



' A. and H., Notes on a Coll. of Nudib. made in India, der Polyceraden, 1883. 

 1863. Bergh in S. R. Hefte xi. and xvi. Id. Beitr. zur Kenntn. - Bergh in S. R. Hefte xi., xvii., and in Harvard Bull, of 



der JapanischenNudibr. 1880. Id. Beitr. zu eirier Monographie Camp. Zoology, 1894. 



