332 ME. A. E. SHIPLEY ON THE GBIfFS SIPUNCTJLTJS. [Apr. 18, 



(2) Selenka, E. — Die Sipunculiden. Eine systematische Mono- 



graphie. Eeisen im Archipel der Philippinen, Bd. iv. 

 Abth. 1. 



(3) Waed, H. B. — " On some Points in the Anatomy and 



Histology of Sipiuicidus nudus, L." Bulletin of the Museum 

 of Comparative Zoology at Harvard College, vol. xxi. 

 No. 3. 



(4) DAXiELSSEif and Koeeji'. — Gephyrea. Den Norske Nordhaus- 



Espedition. Part iii. 



EXPLANATION OF THE PLATES. 

 List of Reference Letters. 



a. Mouth. 0. Sinuses in the same. 



b. Anus. p. Scales on the introvert. 



c. Oesophagus. q. Papilla on scales. 



d. Intestine. r. Rectam. 



/. Nepiiridia. s. Eectal tufts. 



g. Retractor muscles. t. Ducts of rectal tufts. 



h. Brain. u. Mesenteries supporting these ducts. 



i. Digitate process of Brain. v. Sinuses in wall of rectum. 



j. Ventral nerve-coi'd. w. Spindle muscle. 



k. Dorsal blood-TCssel. x. Ciscum on intestine. 



I. Longitudinal muscles. y. Diverticida of dorsal vessel. 



m. Circular muscles. z. Ciliated pit leading to brain. 



n. Tentacular fringe, 



Plate XXV. 



Fig. 1. View of a Sipunculus indicus cut open by aia incision a little to the 

 right of the dorsal middle line. The introvert is extended and the 

 viscera are exposed in situ. The drawing is § the natural size. 



2. A portion of the same in the region of the oesophagus, magnified two 



diameters, to show the numerous bands of longitudinal muscles. 



3. Two views, magnified, of the brain of Sijmncuhts tesseUatiis. The fig. 



to the right shows its position above the oesophagus and between 

 the dorsal retractors. The fig. to the left is more highly magnified, 

 to show the character of the digitate processes. 



Plate XXVT. 



Fig. 4. A view of the head of S. indicus. The mouth is shown in the centre, 

 and between it and the ring of tentacles run several vascular ridges. 

 To the right are two sketches, more highly magnified, to show the 

 characters of the scales on the introvert and the square areas in 

 the trunk. 



5. A dorsal view of the head of S. nudus with the tentacular fringe very 



much folded, X 4. The mouth is away from the spectator and the 

 depression leading to the brain is near him. 



6. A ventral view of another specimen of S. nudus, in which the fringe is 



not at all folded, the wall of the oesophagus is bulged forward and 

 obliterated the oral orifice. 



7. An anterior view of the mouth of <S'. tessellatus. 



8. A longitudinal section through the skin of the introvert of S. indicus, 



showing the structure of the scales, the prolongations of the body- 

 cavity into them, and the ' papillas.' 



9. A view of the rectum of S. tessellatus, showing the anal tufts, the 



enlargement of the alimentary canal to form the rectum, the spindle 

 muscle, the muscular strands supporting the intestine, the cfficum 

 opening into the latter, and the longitudinal and circular muscles of 

 the skin. 



