Dr. W. C. M'Intosh on Pelonaia corrugata. 415 



tubes of Pectinaria helgica, tlic test is little affected by hydro- 

 chloric acid or caustic potash, the former only disengaging a few 

 bubbles of gas from some calcareous fragments, the latter ren- 

 dering the basis structure more translucent, but not destroying 

 its cohesion. Such an investment, as usual, is calculated to 

 restore the shape of the animal, by whatever means alteration 

 is brought about. In the smaller specimen the transverse 

 wrinkles were very distinctly marked, encroaching even on the 

 bulbous end. So firm was the test in the latter, that very con- 

 siderable pressure produced no alteration. The test, however, 

 varies much in this respect in different examples. 



The hairs are evidently essential parts of the test of the ani- 

 mal, like those of Ci/nthia ampulla. Microscopically, they pre- 

 sent a rugged, semiopaque, fibro-granular aspect, having a 

 hyahne basis structure containing many granules, with granular 

 debris of mud and sand attached to it. The sand-particles were 

 often largest at the base of each process; and the edges were 

 rough from projecting threads of the basis structure with 

 adhering debris. On the whole, the process was much finer 

 than that of CyntJiia ampulla, which, under the same power 

 (350 diam.), showed a great increase of coarse sand-particles, 

 Diatomacese, sponge-spicula, and Foraminifera, together with 

 Crustacean and Annelidan hairs, shells of Cyprides, and other 

 debris. 



Underneath the external matrix of the test generally is a 

 layer of interlaced broad fibres, which cross each other at right 

 angles, the longitudinal ones being somewhat fasciculate, the 

 circular less so. The individual fibres (fig. 4) are of large size 

 and faintly striated longitudinally, and some contain traces of 

 nuclei. At some parts a cellulo-granular texture is incorpo- 

 rated with the layer, the fibres in that case following for the 

 most part one direction, and leaving intervals between the fasci- 

 culi, in which the cellulo-granular structure is situated. This, 

 however, may have been due to the ordinary epithelial lining of 

 the layer superseding it. This muscular coat is very easily se- 

 parated from the whitish internal surface of the test in spirit ; 

 and in the fresh specimen it is scarcely more difficult, with the 

 exception of the narrow j)ortion, where the fibres adhere to the 

 test more firmly. It is also proportionally thicker in the latter 

 region. The general appearance of the layer is shown in 



On removing the soft pinkish textures from the test, the 

 appearance is as represented in fig. 2, a great portion of the 

 body of the animal being occupied by the branchial apparatus, 

 which lies within the muscular coat. When minutely examined 

 with the naked eye or a lens, this structure is found to be ribbed 



