and Species of Nudihranchiate Mollusca. 143 



twenty-five laminae ; they are retractile within cavities, the 

 margins of which are produced into short sheaths. The branchiaj 

 are small, slender, bushy, dividing dichotomously, and arising 

 from six roots, three being at each side of the anus ; there is 

 a considerable interval between the anterior roots ; and the 

 posterior ones bear numerous and smaller plumes. The anus, 

 situated almost between the last, is wide and tubular, and has 

 the posterior wall more produced than the anterior. The 

 common cavity, into which the branchias and anus are re- 

 tractile, has the margin raised. The mouth is subterminal, 

 opening rather downwards 5 on each side is a conspicuous pit, 

 into which it is possible that a small tentacle may be retractile 

 by invagination. The foot is linear, with a wavy edge, ante- 

 riorly lobulated inwards. The colour of the spirit specimens 

 is a brownish cream or pale fawn, sparingly marked with 

 whitish, tubercular, or slightly raised, unequal, rounded, ocel- 

 lated spots, which are rather more numerous on the sides ; a 

 row of five or six of these spots extends along the medio- 

 dorsal line from in front of and between the dorsal tentacles ; 

 tlie margins of the branchial and tentacular cavities are sur- 

 rounded by a row of such spots. 



Dimensions (in spirit) : length 48 millims., breadth 15, 

 height 18, length of tail 9. 



Hah. Australia. 



C. hrevicaudatum presents many points of resemblance to 

 the following species {G. ohlongum). 



Ceratosoma olhngum, sp. nov. PI. VII. figs. 7, 7 a, 7 b. 

 C. elongato-oblongum, prismaticum, Itere, fuseum, nigrescentibus 

 maculis rotundatis sparse ornatum; dorso oblongo, iion lobato et 

 non levato; tumore postbranchiali parvo, rotundato, uodulari ; 

 Cauda brevi ; tentaculis dorsalibus parvis, conicis, acutis, arrectis, 

 lateraliter compressis, in cavitates retractilibus ; branchiis 18 + , 

 ramosis, ex sex radicibus orieutibus, ante anum circulariter positis, 

 in foramen commune retractilibus ; pede lineari. 



The body is oblong, smooth, prismatic, not raised in the 

 branchial region ; the dorsal surface is rather curved, and 

 shows but little trace of constriction or lateral lobation. The 

 postbranchial protuberance is small, rounded, and nodular ; 

 and between it and the origin of the short subconical tail 

 there is but a very small interval. The dorsal tentacles are 

 conical and pointed, laterally flattened, diagonally laminated, 

 directed rather forwards and outwards, and retractile witliin 

 cavities. The branchiae are about eighteen in number, slender, 

 and placed in a semicircle in front of the anus ; tliose at the 

 sides are rather longer. The four anterior, with an interval 

 between the two foremost, arise separately ; the others, six on 



