PREFACE vii 



tall of Mliicli had already been included in the keys as forms 

 expected to occur within the British area, viz., Odontaster 

 mediterrayietis, Gastraster margaritaceus, and Oj^hiochondrus 

 armatus. Furthermore, after the work was completed, some 

 small sea-stars were received from Mr. Farran, among which 

 were two more species new to the British fauna, viz. Hoplaster 

 spi72osus and PediceUaster typicus. (Cf. Appendix.) These two 

 species also had already been included as likely to occur within 

 the British area. 



While the book has thus become much more extensive than 

 the original Danish work, comprising, in fact, the whole of the 

 echinoderm fauna known from the north-east Atlantic, the 

 general plan and scope of the work remain the same — its main 

 object being to offer an easy means of identifjdng with certainty 

 the various forms of echinoderms known from, or likely to occur 

 in, the British seas, through precise descriptions, kej^s, and 

 figures, illustrating partly the general appearance of the species, 

 partly the finer details necessary for their determination. 

 Literary references are usually not given under each separate 

 species ; anyone washing to go deeper into the scientific details 

 will find the more important literature quoted in the list of 

 literature given at the end of the book. The author has done 

 his best, Avithout reducing the claims to scientific exactness, to 

 give the work such a form that no special zoological training 

 should be necessary for using it ; the index to the unavoidable 

 technical terms, given at the end of the book, may prove useful 

 in this connection. For the same reasons, finer anatomical 

 details have been omitted when not necessary for the deter- 

 mination. It may also be pointed out that in several cases the 

 family diagnoses have been made to fit especially the forms 

 occurring in the north-east Atlantic region, when, namely, if the 

 diagnoses had to fit all the forms belonging to such a family 

 known from the whole world, it would necessitate going too 

 deeply into details difficult to observe and needing a very detailed 

 explanation. 



Thus it is hoped that all reasonable claims are fulfilled for 

 making the book useful, not only to zoologists proper, but also 

 to amateurs. The author would, indeed, like to call the attention 



