348 Transactions. — Zoology. 



DESCEIPTION OF PLATES XXXI.-XXXIV. 



Plate XXXI. 



Fig. 1. Pull-grown specimen, stalk cut of!. 



Fig. 2. Specimen nearly full-grown, having spinous and oblong processes 

 on the test. 



Figs. 3 and 4. Young specimens. Fig. 4 is very young, the spines begin- 

 ning to develope. 



Fig. 5. Specimen having a bivalve imbedded in the test. 



Fig. 6. The right half of the test is cut away. Notice the muscular 

 bands of the body and the interlacements between them. 

 Notice also the blood-vessel to the test on the right (cut). 



Plate XXXII. 



Diagrammatic view, with the test and body-wall of the left side 

 removed. 



The cut body-wall is represented by the double line between endostyle 

 and test, &c. The branchial sac is shown with part of its left wall cut away 

 to show the ring of tentacles and dorsal tubercle. The folds of the right 

 side are represented as seen. A bristle is passed from the interior of the 

 body out through the branchial aperture. 



Plate XXXIII. 



Diagrammatic view of the body from the right side, the body-wall of 

 the right sic^e and the right half of the test being removed. The cut 

 body-wall is represented by a double line, as in Plate XXXII., and the 

 branchial sac is shown cut open as before. A bristle is passed out 

 through the branchial aperture, as in Plate XXXII. 



Plate XXXIV. 



Fig. 1. The body- wall of the right side is removed. Note, as in figs. 2 

 and 3, the black line drawn across the body-wall in the neigh- 

 bourhood of the anus. This represents the point to which the 

 lining invagination of the test is carried from the atrial aper- 

 ture. The terminal end of the intestine is shown projecting 

 from beneath the branchial sac, to its left. 



Fig. 2. The right wall of the branchial sac is cut away. A bristle is 

 passed out through the branchial aperture. 



Fig. 3. The branchial sac is removed, also the right half of the ring 

 of tentacles. 



Fig. 4. The body is opened along its ventral aspect, the sides thrown 

 back, and the branchial sac removed. In this sketch the 

 muscles of the right half of the body only are shown. The 

 liver is cut away, the stalks being represented on the stomach. 

 The lining invagination of the test in the atrial aperture has 

 been removed. 



Fig. 5. Transverse vertical section of the body near the atrial aperture. 

 This sketch shows the relations of the atrium. The atrial in- 

 vagination is shown shaded dark. The cut is made at the 

 point where the intestine turns at right-angles to its former 

 course, to end in the anus. 



