262 Mr. J. Alder on Euplocamus, Triopa and Idalia. 



Mr. Thompson's drawings and these specimens is certainly very- 

 great, though the anterior end in mine is rather more closed than 

 in his, by the bending over of the edges through which the ten- 

 di-ils of the two sides have become entangled together. None of 

 the markings are so strong as in the figures, the transverse mark- 

 ings on the broad flat sides being scarcely perceptible in any of 

 the specimens, and the striae on the flattened edges not extending 

 in general very far from the posterior end, where they are in some 

 specimens tolerably strong and extend over the inner edge of the 

 rim as shown in the figure. The dimensions in length, at least 

 of my specimens, were all less than those of Mr. Thompson, viz. 



Extreme length 4 inches. 



Width H „ 



Thickness rather more than \ „ 



The colour when fresh was a pale horn as usual, but becomes 

 brown by keeping. 



As regards the period of protrusion, from May when I procured 

 my first specimens until the end of November and beginning of 

 December the fish became scarce, when they again appeared in 

 the market, and on the 27th of December I procured some fresh 

 eggs, one pair of which was said to have been taken from a large 

 female then lying opened before me. Others I saw subsequently, 

 and in one I observed the ovaries to contain eggs still in a soft 

 state and without their covering ; this was a large specimen, mea- 

 suring 28 inches. There can therefore be no doubt that the eggs 

 of these fishes are protruded at least at two periods of the year. 



XXXVII. — Note on Euplocamus, Triopa and Idalia. 

 By Joshua Alder, Esq. ' ' 



I In the second volume of the ' Enumeratio MoUuscorum Sicilise,' 

 Dr. Philippi under the head of Idalia (to which he now refers his 

 genus Euplocamus) makes some strictures upon a notice that ap- 

 peared in this Journal (vol. vi. p. 217) from Professor E. Forbes, 

 stating that the lateral appendages of Euplocamus of Philippi 

 {Triopa of Johnston) had no vibratile cilia, and consequently were 

 not branchial. The same notice also stated that the lateral ap- 

 pendages of Tritonia and Eolis were ciliated, but the branchial 

 appendages of Polycera were not so. 



To these observations Dr. Philippi makes several objections. 

 In the first place, after asking on what species of Euplocamus the 

 observations were made, he says that a mere inspection of the 

 figure of his E. croceus, without any microscopic disquisition, 

 will show that the lateral appendages serve the office of respira- 

 tion, and from this species, he adds, the transition is evident to 



