FASCIOLES. 



Among the Spatangoids there are several families where the spines are 

 specialized along certain lines (the so-called fascioles or Semites) in which 

 they always retain embryonic features, being either articulated j. IG 8 

 {Fig. s) or directly attached to the test, and provided at the extremity $!jjj 

 and along the shaft with a more or less sensitive vibratile membrane, as 

 all young spines originally are. These fascioles are very varied in their 

 course ; they extend round the petals, in which case they are called 

 peripetalous, as in Brissopsis {PI. XIX. f. 7-0 ; PI. XXI. f. 2), Brissus 

 {PI. XXI". f. 1), Metalia {PI. XXI f. 5; PI. XXP. f. 4; PI. XXP. 

 f. s), Rhynobrissus {PI XXIII". f. o), Meoma {PI XXII. f. 3). 

 The subanal plastron, as it is called, is edged by a fasciole which 

 encloses within its area a part of the inner poriferous zone of the 

 actinal posterior lateral ambulacra : this is called the subanal fasciole, 

 as in the case of Brissopsis, of Maretia {PI. XIX h . f. s), of Lovenia {PL 

 XIX\f. 2), of Spatangus {PI XIX'. f. 0), of Metalia {PI. XXP. f. 5), and 

 of Rhynobrissus {PI. XXIII a . f. 4). In other genera there is connected 

 with the peripetalous fasciole a band running towards the posterior ex- 

 tremity, bending downwards, and passing under the anal system ; this is called 

 the lateral fasciole. It occurs, among other genera, in Agassizia {PI. XIX". 

 f. 1, 2), in Linthia {PI. XIX". f. 7, 8; PI. XXP. f. 5, 7), in Tripylus {PI. 

 XXP.f. 4), in Schizaster {PI XXIII". f. 1, 3), in Moira {PI. XXIII. f. 5, e). 

 The lateral fasciole is sometimes disconnected from the peripetalous fasciole, 

 the portion which passes under the anal system alone remaining ; or when 

 there is no distinct subanal plastron formed, the subanal fasciole remains open : 

 the first case occurs in Faorina, the latter in Meoma {PI. XXIII f. 4) and 

 in Linthia. It is then called the anal fasciole. An anal fasciole is also 

 sent off as a branch of the subanal plastron (Brissopsis), and may or may not 

 enclose the anal system. The subanal fasciole of Rhynobrissus is subdivided 

 into two areas by a transverse fasciole. The anterior part of the peripetalous 

 fasciole of Faorina {PI. XIX". f. 4) is double, and encloses a secondary area. 



In Echinocardium {PI. XX. f. 1,5), Breynia {PI. XV". f. 7), and Lovenia 

 {PI. XIX c .f. 1) we find a still different kind of fasciole, — an internal fasci- 



