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



Mr. Thompson's drawdngs 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'ds of the two sides have become entangled together. None of 

 the markings are so strong as in the figm-es, the transverse mark- 

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

 the specimens, and the stri?e on the flattened edges not extending 

 in general \'ery far from the posterior end, where they are in some 

 specimens tolerably strong and extend over the inner edge of the 

 rim as sho^vn in the figm-e. The dimensions in length, at least 

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



Extreme length 4 inches. 



Width 11 „ 



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 imtil 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. 



XXXYII. — Xote on Euplocamus, Triopa and Idalia. 

 By Joshua Alder, Esq. 



In the second volume of the ' Enumeratio jMoUuscorum Sicihae,' 

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

 genus Euplocamus) makes some strictm'es 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 cihated, but the branchial 

 appendages of Pohjcera were not so. 



To these observations Dr. Philippi makes several objections. 

 In the fii'st place, after asking on what species of Euplocamus the 

 obsenations 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 respii'a- 

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



