274 LETTERS EEOM C. DAHWIK, ESQ., 



head), containing the testes, vesiculse, and penis. In male Ibla 

 we have hardly any cirri or thorax ; in some male Scalpellums 

 no mouth; here both negatives are united. I know it to be the 

 male of Alcippe from absolute identity of the pupse of both sexes 

 and other reasons. I believe the males occur on every female. 

 In one case I found twelve males and two pupae on point of 

 metamorphosis permanently attached by cement to one female ! 



Excavation of Burrow. — The outer skin, and even the whole 

 thickened edge of the orifice into the sack, with its strong sharp 

 spines, is periodically and often moulted. There is a great differ- 

 ence in the state of the star-headed spines on the new underlying 

 and the old worn spinel on the old membrane. This being the 

 case, and there being good motive power in the long and trans- 

 verse and adductor muscles, I do not doubt the excavation is 

 wholly mechanical. From the position of the larval antennae, 

 Alcippe after metamorphosis must occupy a position fully as much 

 inclined, or more inclined, than as drawn, "^^ and so would with 

 only little change assume the position which it holds in the shell. 

 Though I cannot demonstrate I can show good reason to believe 

 that it moves its position, when first boring into the shell, just 

 as Lithotrya does, a row of horny discs representing the calcareous 

 overlapping discs in that genus. 



With respect to the edging or rim of shell observed by you, it 

 is quite inorganic, and has no more relation to Alcippe than the 

 main part of the supporting coral-reef has to a coral. When 

 dissolved in acid it is found to contain all sorts of rubbish, even 

 of foreign animals. It is a kind of natural mortar. 



The rudely radiating dark lines and punctures in the shell 

 over the peduncle of Alcippe are formed by a minute Annelid. 



Affinities. — I am dreadfully puzzled, and every day change, 

 whether to form a family for its reception, as in one point of view 

 it amply deserves, or to be guided by its varied close affinities to 

 several genera amongst the Lepadidse and place it in that family. 

 I have never repented in placing Anelasma there ; but what to 

 do in this far more puzzling case I cannot yet tell. 



I fear my long rambling letter will puzzle and weary you. 



• Sketch, given in letter. 



