JOURNAL 



OF THE 



ROYAL MICROSCOPICAL SOCIETY. 



DECEMBER, 1880. 



TRANSACTIONS OF THE SOCIETY. 



XXIV. — On some Sti'uctural Features of Echinosirej^Jius molare, 



Parasalenia graliosa, and Stomojmeustes variolaris. 



By Chaeles Stewaet, M.E.C.S., Sec. E.J\I.S. 



(JRead 10th November, 1880.) 



Plate XX. 



EchinoBtreplius. — This genus differs from all other Desmosticha 

 in the form of its corona, which is broadest near the abactinal pole, 

 with the mouth situated at the extremity of the opposite, more 

 pointed, region. The flattened abactinal surface bearing spines far 

 exceeding in length those of other parts. 



These exceptional features give greater interest to the other 

 points in its structure, which, in some respects, are as remarkably 

 difi'erent from other forms as the coarser characters. 



Genital glands. — These are abundantly crowded with spicula, 

 those in the parts of the branches nearest the common duct being 

 in the form of perforated plates, often of large size, and identical 

 in all respects with those found in the genus PhyUac<(nthus 

 amongst the Cidaridae; but mixed with these, and replacing them at 

 the tips of the branches, are numerous bihamate spicula, such as are 

 so widely distributed amongst the Echinometradae and Echinidte. 

 The greatly varied spicular forms in Echinometra lucunter some- 

 what approach to this condition, but in it the perforated plates 



explanation op plate XX. 



Fig. L — Portion of genital gland of Echinostrcphns molare. 



„ 2. — Si(](! vifw of jiiw of geminiform pedicellaria oi Echinostrephus. 



„ S. — Ditto viewed fi'Am witliin. 



„ 4. — Jiiw of ophioce])li;tlons \^(ii\\cc\\;ma, oi Echinostrephus. 



„ 5. — Jaw of tridact\ le pfdioelluriii of Echinostrcjihus. 



„ 6. — Sido view of jaw of gemmiforiii pedicellaria of Parasalenia. 



„ 7. — Ditto viewed from witliin. 



„ 8. — Spicula from aml)td:icial tulie of Parasalenia. 



„ 9.— Jaw of n|ilii()Oipliulou.s pi dicellaria of Slomnpncustcs. 



„ 10. — Jaw of tridartylc |)eilii-ellaria of I'^tomojmeustc.t. 



No. S niiignifle.l :;".:; cii:mi , tlio rest 7,'i diam. 

 vol . 111. ':) V 



