REPORT ON THE OPHIUROIDEA. 353 



PLATE XXXVI. 



(All the figures, except 19, are from very young specimens. For further remarks on 



this plate, see generic description of Gorgonocephalus.) 

 Fig. 1. ijt'. GorgofiocejjJialus agassizii, Tiym. A very young individual, having a disk 

 little more than 2 mm. in diameter, seen from below. In the inner portion 

 of the right lower interbrachial space there should be a small pimple, — the 

 madreporic shield, or plate. All other plates of the lower surface are 

 concealed by the skin, though those of the back are distinct. There is, as 

 yet, but one full fork to the arm, and the beginning of a second. Curved 

 tentacle scales are continued quite to the base of the arm. The fewness of 

 the forks and their distance from the disk bring to mind Trichaster. 



„ 2. ^^. Two mouth angles and the beginning of an arm of a very young specimen, 

 dried ; side mouth shields {b). 



„ 3. 2j^. The same specimen seen from above, with the base of an arm. On the 

 back of the disk may be seen the primary plates (g) with lines of granules 

 between them ; and scales along the edge of the disk and on the upper side 

 of the arm. 



,, 4. \^. Tip of arm of a young specimen. The side arm-plates (?') are already 

 formed, and the hooks. 



„ 5. Y- The same, from above, with two additional joints. The side arm plates 

 (^) still occupy the whole surface ; but, on the central line, a small scale, 

 homologous with the upper arm plate, is just forming. Later, it adds to 

 itself many similar scales. (See fig. 15.) 



,, 6. \°. Lower surface of an arm near tip of a twig, showing the side arm plates, 

 bearing their hooks. This and the other figures of arm joints represent 

 preparations dried to show the details of the plates. 



„ 7. \^. Upper surface of a joint from near the tip of a twig, showing the side arm 

 plates, and, between them, thin irregular scales, the homologues of an upper 

 arm plate. 



,, 8. ^^. A side arm plate in profile, near the tip of a twig, bearing its hooks. 



,, 9. */*. A side arm plate, in profile, near the tip of a twig, showing some grains 

 near its edge ; also a simple hook, which will later be mounted on a grain. 



,, 10. ^{\ Two joints in profile, somewhat further in than fig. 9. The arm has 

 already risen considerably above the side arm plates (i) which boar, on their 

 outer edge, tentacle hooks or scales (q) and, above, two grain hooks ; while 

 on the body of the arm are three more grain hooks. 



„ 11. ij^. Arm joint in profile, two forks from the tip, and more developed than in 

 fig. 10. The tentacle hooks (q) have grown thick; and the grain hooks have 

 left the side arm plate (?"), and stand only on the arm grains. 



