283 MR. H. N. MOSELEY ON TWO NEW 



Where it is simple it is thin and flexible, hut in certain spots it is strengthened and 

 rendered stiff by the presence in it of rounded or plano-convex masses or plates of denser 

 tissue, which are tough and cartilaginous in consistence, and which are disposed oyer the 

 surface of the test in a nearly symmetrical manner. These plates are extremely con- 

 spicuous when the test is held up to the light and viewed by transmitted light, because 

 they refract the light strongly; and the pattern formed by them on the test when 

 thus viewed has a very peculiar appearance. The disposition of the plates on the 

 ventral surface' of the body will be seen from fig. 1, that on the dorsal surface from 

 fig. 2. 



A series of globular lobes range on either lateral margin of the body, and give it here 

 considerable rigidity, and a. ridge of slightly condensed tissue runs across the body at 

 the upper margin of its dorsal surface. A series of flattened plates is disposed over the 

 inferior region of the ventral aspect of the body, whilst the superior region of the same 

 aspect, covering the gill-sac and perforated by the inhalant aperture, is entirely devoid of 

 plates, very thin and flexible, and most perfectly transparent. On the dorsal aspect of 

 the body a very large plate occupies the middle line inferiorly, whilst immediately above 

 it two pairs of oblong plates (fig. 2, d) form a stiff shield for the principal viscera, which 

 lie upon them. Two series of oval plates range on either side of the larger median ones, 

 and extend up as far as the exhalant aperture. The test-tunic is continued downwards 

 from the upper region of the body to form the outer wall of the cylindrical stem, thus 

 forming a tube. The lower end of this tube is widened out into a funnel-shaped mouth, 

 and in the specimen had apparently been torn away from some object of attachment. 



The substance of the test is composed of transparent hyaline tissue, in which are 

 embedded the small bodies represented in fig. 4, the larger of which have a length of 

 from *007 to "014 millim. They are irregular in form, sometimes crystalline, or with 

 apparently crystalline contents. They are not sensibly altered in appearance by the 

 action of acetic acid, and no effervescence is produced in the test-tissue by that re- 

 agent. The bodies are present in the greatest abundance in the test-tissue at the base 

 of the stem. In the plates of denser tissue they are rather less abundant than else- 

 where. The test forms a simple sac continuous with the tubular cavity of the stem. 



The exhalant orifice is an aperture in the test situate at the end of a short tube projecting 

 externally on the dorsal aspect just below the nerve-ganglion. Into it the ducts of the 

 generative glands and the rectum open. The inhalant aperture was entirely obliterated 

 in the only specimen obtained ; it must have lain on the ventral aspect of the body, 

 since the dorsal wall was intact. The arrangement of the muscular fibres and remnants 

 of attachment of the gill-sac seemed to indicate the position for it given in the figure, 

 where it is introduced conjecturally. 



Closely attached to the inner surface of the test-wall is a delicate tunic (the mantle) 

 containing muscles. The muscles occur in the form of very fine bands, which have 

 a nearly parallel course. The series of bands springing from near the region occupied 

 by the heart follow the curved inner surface of the test-cavity towards its superior 

 margins. The muscles are disposed most thickly in the lateral regions. The mesial 

 region of the dorsal surface is entirely devoid of them, but they extend over the whole 



