220 Rev. T. Hincks on the 



boundary of the cell. The pointed mandible of the avicula- 

 rium is directed upwards. At the same time the elevation 

 of the peristome has been proceeding, and a secondary orifice 

 has been formed which differs widely from its predecessor. 

 The subsequent changes, which produce a marked effect on 

 the appearance of tlie species, are in great measure due to the 

 progress of calcification. The new features which have been 

 added are to a large extent obliterated by the rapid accretion 

 of calcareous matter. The pells lose their convexity, the 

 sutures all but disappear, the punctures become indistinct, 

 the orifice on which the aviculariura was developed is no 

 longer on the surface, but deeply sunk beneath it, and at last 

 the avicularium becomes undistinguishable. The adult orifice 

 is rounded above and produced in front into a rather long 

 pointed sinus (PL XIV. fig. 1). In the more advanced stages 

 of growth a dull, minutely granulose, flatfish crust covers the 

 zooecia. The structural elements to which most interest 

 attaches are probably the sinus on the secondary orifice and 

 the associated avicularium. Their development proceeds pari 

 passuy and the shape of the sinus is more or less determined 

 by the avicularium. 



In this case the sinus seems to be simply a provision for the 

 reception of the avicularium, and, indeed, it is probable that it 

 is in large measure due to the growth of the avicularium along 

 the edge of the secondary orifice. It has therefore a distinc- 

 tive significance and is not comparable with the (apparently) 

 similar structure amongst the Myriozoidas. The development 

 of Escharoides rosacea, Busk, runs parallel to that of the 

 present species *, and its structural features are almost iden- 

 tical. 



I think we may recognize in Escharoides the characters of 

 a natural group. 



E. Sarsii appears to be abundant in the St. Lawrence and 

 generally in the northern and arctic seas. It forms large 

 coral-like growths composed of many massive branching seg- 

 ments springing from a common base, foliated, contorted, 

 expanding upwards, and terminating above in numerous 

 smaller segments. 



Range. Antarctic seas {Sir J. Hooker) ; Tromso, 20-60 

 fath. {Sars) ; Spitzbergen, Greenland, Nova Zembla (Smitt^ ; 

 Jan May en {Lorenz) ; Kara Sea^ 49-65 fath. {Levinsen}. 



* ' Britidli Marine ruU'zoa," i. pp. Z'37, S38. 



