112 



THE AMERICAN NATURALIST [Vol. XLIII 



in color. The figures are intended to illustrate not only the 

 new forms described, but also previously known species that 

 have not been figured and some others, figures of which will 

 be of service to the student. In a number of instances the 

 nomenclature has been changed, and has been placed on as 

 firm a basis as possible by the use of the generally accepted 

 principles of the International Code. It will be seen that the 

 monograph has a wider scope than a systematic revision, in- 

 cluding as it does accounts of the anatomy, embryology and 

 physiology. 



The interesting account of the history of the classification of 

 the two families is followed by an important consideration of 

 the characters used in classification, and a discussion -.of the 

 subfamilies and leading genera. Twenty-nine genera. of which 

 8 are new, are accepted, distributed as follows: Synaptiine, 11 

 genera (2 new) comprising 60 species; Chiridotinae, 7 genera 

 (3 new) with '2'2 species-. Myriotrodiina:'. 3 genera, 6 species; 

 Molpadiiche. 8 genera (3 new and 1 new name) with 46 species. 

 Dr. Clark has discovered that Ankyroderma is practically a 

 juvenile condition of Trochostoma. As generally defined the 

 former is distinguished from the latter by the presence of 

 rosettes of racquet-shaped rods from the center of which there 

 extends outward a conspicuous anchor. It was found, from a 

 study of more than 3f)0 specimens of these two genera, that the 

 presence of anchors and rosettes of racquet-shaped rods can 

 not be regarded as even a constant specific character. For ex- 

 ample, small specimens of Trochostoma intermedium Ludwig 

 with very thin skin are clearly Ankyroderma. Large specimens 

 have a rather thick body wall and very numerous deep red or 

 brown bodies in the skin, but no rosettes. The rosettes dis- 

 integrate into heaps of rounded colored bodies which differ 

 from calcareous plates or particles in being chiefly phosphoric 

 acid and iron. They are therefore quite unlike the ordinary 

 calcerous deposits of holothurians, and are named "phosphatie 

 deposits." 



"As to the significance of these facts our knowledge is as yet too 

 imperfect to draw any clear conclusions. Chemical analysis 2 of the 

 2 The composition of these bodies is given as FeP0 3 + 4H 2 = 66.2, 

 Pe (OH), = 20.2 and CaC0 3 = 6.4. There is also probably Mg present. 

 ~. "I!!.* 180 reas ° n . to beUeve that the amount of CaC0 3 is subject to 

 3 particles are first transformed 

 nportant substance present, and 



