166 



LOWER INVERTEBRATES. 



Echinothuridae. Cidaris metularia occurs in the Pacific and East India oceans, C. 

 thouarsii on the west coast of North America, and G. tribuloides on both coasts of 

 the Atlantic. Fine specimens of the latter measure five inches across the spines. 

 Dorocidaris papillata occurs at depths of from one hundred to six hundred fathoms, and 

 has extremely long fluted spines, so that an example with a test about an inch across 

 will measure eight or nine inches from tip to tip of spines. It occurs in the Mediter- 

 ranean, and the Atlantic, while examples collected at the Philippines cannot be dis- 

 tinguished from it. D. bracteata, a Pacific species, has the flutes of the spines set with 

 serrations. 



In the species of Phyllacanthics the spines are often ornamented with frill-like 

 lamellae, but vary greatly in shape and decoration. P. gigantea, of the Sandwich 



Islands, has ten 

 spines in a series, 

 and six or eight 

 lamellae on each 

 spine. Gonioci- 

 daris canalicula- 

 ta is a species with 

 elegant spines, 

 tolerably abun- 

 dant in the south- 

 ern ocean. It has 

 been dredged in 

 sixteen hundred 

 fathoms. In this 

 species the upper 

 part of the test is 

 quite flat, and the 

 two first series of 

 spines, which are 

 much larger than 

 the spines of Cid- 

 aris usually are on 

 that part of the 

 test, lean over to- 

 wards the anal 

 opening, and form 

 an open tent for the protection of the young. These spines are cylindrical and 

 nearly smooth, the outer series longer. and shorter than the inner. A somewhat 

 similar arrangement obtains in Cidaris nutrix. Sometimes the young creep out, 

 with the aid of their first few pairs of suckers, upon the long spines of the mother, 

 and return to the marsupium. 



Porocidaris purpurata has several rows of peculiar paddle-shaped spines round the 

 mouth. These spines are flattened, longitudinally grooved, and serrated upon the edges. 

 Qoniocidaris florigera is remarkable for the shape of the primary spines set around 

 the anal area. These spines are dilated at the tip in such a manner as frequently to 

 form a flattened cap, equalling in width one-third the diameter of the test. The oldest 

 species of Cidaris occur in the Trias, and are small forms with smooth tubercles. 



Fig. 145. — Cidaris nutiix. 



