GENUS ASP ID ISC A. 



793 



Aspidisca lyncaster, Stein. Pl. XLV. Figs. 23 and 24. 



Body ovate, rounded on the right side and at the two ends, the anterior 

 border of the left side incised so as to produce a posteriorly directed 

 spur-like projection, a similar aculeate spur, curved slightly outwards, pro- 

 jecting from the ventral surface of the carapace on the same side, within a 

 short distance of the posterior margin ; ventral styles short and thick, 

 seven in number ; five anal styles ; endoplast band-like, curved ; contrac- 

 tile vesicle single, situated a little in advance of the anal styles. Length 

 of body 1-450" to 1-360". Hab. — Salt water. 



Aspidisca lynceus, Ehr. 



Body ovate, widest and somewhat truncate posteriorly; the marginal 

 border of the carapace entirely even, the left one straight, the right one some- 

 what convex ; the dorsal surface smooth, or marked longitudinally with three 

 feeble furrows ; the inferior surface bearing seven ventral and five anal styles. 

 Length of body 1-540". Hab. — Salt water. 



Aspidisca turrita, C. & L. Pl. XLV. Figs. 31-33. 



Carapace suborbicular, widest and somewhat truncate posteriorly, its 

 marginal border entirely even, the left side nearly straight, the opposite 

 one rounded, a thorn-like recurved spine developed from the centre of the 

 dorsal surface ; ventral styles as in ^. lynceus. Length 1-450". 



Hab. — Sea water. 



Aspidisca polystyla, Stein. 



Carapace oval, its margin entire, the left side border nearly straight ; 

 the dorsal surface slightly convex, traversed by three longitudinal grooves ; 

 ventral styles seven in number, forming two anterior, oblique, parallel rows 

 of three each, the seventh style stationed by itself to the right and rear of 

 the other six ; anal styles from ten to twelve in number. Length 1-5 10". 



Hab, — Sea water. 



This species, by reason of the greater number of the ventral styles, has formed 

 the type of Stein's sub-genus OnycJiaspis and, in connection with the last-named title, 

 has been elevated by Diesing * to the rank of an independent generic group. 



Aspidisca hexeris, Quenn. 



Carapace elliptical, about one and a half times as long as broad, 

 equally rounded at each extremity; the right-hand border armed, close 

 behind its centre, with a single, backwards directed, spur-like projection ; 

 ventral styles short and thick, seven in number; six anal styles. Length 

 1-500". Hab. — Salt water. 



Aspidisca sedigita, Quenn. 

 Body broadly ovate, suborbicular, the right border smooth and rounded, 

 the left one incised so as to produce a central, anterior, and posterior spur- 



* ' Revision cler Froth elminthen,' 1866, 



