REPORT ON THE ECHINOIDEA. 143 



adjoining, placed within the trivium and separated from the bivium by the intercalated 

 interambulacral plates (PI. XXVI." fig. 8). 



The anal pouch (PI. XXVI/ figs. 5, 6) is as in the Pourtalesise strengthened by large 

 irregularly-shaped rectangular plates, and is somewhat triangular when seen from above 

 (PI. XXVI. * fig. 7) ; the opening is well covered by rather stouter spines than are found 

 on other parts of the test. Figs. 2, 4, 7, 12 of Plate XXVI." show the arrangement of 

 the plates of the actinal surface of the test, and a combination of the figures 8, 9, 15, and 

 17, that of the abactinal side of the test. 



The course of the alimentary canal is easily traced in the view of the interior 

 (PI. XXVI.'' fig. 1) from the actinal side, and in the profile of PI. XXVI. fig. 6. The 

 course and the shape of the aHmentary canal is similar to that of Cystechinus. The anal 

 extremity of the canal is remarkable for its small size (PI. XXVI. " fig. 6). 



The largest and the smallest si^ecimens collected are figured natural size on Plate 

 XXVI. The collection also included a couple of intermediate sizes. 



Station 147. December 30, 1873. Lat. 46° 16' S., long. 48° 27' E. ; 1600 fathoms ; 

 bottom temperature, 0"8° C. ; globigerina ooze. 



Station 157. March 3, 1874. Lat. 53° 55' S., long. 108° 35' E. ; 1950 fathoms; 

 diatom ooze. 



*£Ichinocre2yis. 

 Echinoerepis, A. Agassiz, 1879, Proc. Am. AcaJ., vol. xiv. p. 200. 



This genus has, like Pourtalesia, a sunken actinal groove, but the other features of the 

 test difi'er entirely from those of the sjoecies thus far described in this family. There is 

 no anal snout, the anal system though forming a re-entering pouch much as in Pourta- 

 lesia is situated on the actinal side as in Cystechinus. Seen in profile the test is 

 pyramidal (PL XXVII. fig. 3), the apical system is placed about one-third the length of 

 the test from the anterior end ; the anterior part of the test forms a regularly inclined 

 surface sloping rapidly from the apex to the ambitus with sharply rounded corners ; 

 towards the actinal surface and at the median line of the lateral anterior ambulacrum on 

 the upper part of the test, the actinal groove forms a comparatively slight depression 

 on the actinal surface of the anterior edge of the test, but omng to the gradually sloping 

 sides of the edge of the actinal groove, extending from the flat actinal anterior part of the 

 test (PI. XXVII. figs. 5, 7), and taken in connection with the flat sloping test of the 

 anterior extremity and its deep re-entering angle when seen from above, it forms, when 

 seen from the anterior extremity, a groove deeply cut out of the test. As seen from 

 above the anal keel forms a slight arch from the apex to the anal extremity. The median 

 line of the anterior lateral ambulacra is slightly re-entering, forming a deep indentation 

 in the anterior outline of the test as seen from above. 



The very slight re-entering angle of the median line of the posterior lateral aml)u- 



