from the Island of Malta. 271 



Pygorhynchus Vassalli, Wright, n. sp. 



Test oblong, wider behind than before ; interambulacrum pro- 

 duced into a caudal elongation ; petaloid portions of the am- 

 bulacral areas narrow and short; sides tumid; anus small, 

 round, nearer the inferior border than the dorsum, with a 

 projecting beak-like process arching over its upper border, 

 and an oblique truncature of the lower part of the border 

 below; base slightly concave; mouth pentagonal, nearly cen- 

 tral ; oral lobes small ; rays of the poriferous star around the 

 margin short. 



Dimensions. — Antero-posterior diameter l/^ inch, transverse 

 diameter y'oths of an inch, height nearly /(jths of an inch. 

 Most of the specimens average only from one-half to two-thirds 

 of these dimensions. The large specimen before us is the most 

 perfect we have examined. 



Description. — This small Urchin has an oblong form ; it is 

 rounded before, a little enlarged towards the junction of the 

 middle with the posterior third, which is produced into a caudal 

 process. The sides are tumid, and the upper surface is flat- 

 tened ; the petaloid portions of the ambulacral areas are narrow 

 and short, and form only a star on the dorsum ; the single and 

 postero-lateral areas are nearly alike in width and length ; the 

 antero-lateral pair are rather wider and shorter, they are /^th* 

 of an inch in length, and are slightly curved forwards and 

 outwards ; their poriferous zones contain eighteen pairs of 

 pores, arranged in narrow rows, and not united by any apparent 

 slit. The postero-lateral areas are 2^0^^^ ^^ ^^ i^^^ i^ length, and 

 their zones contain twenty pairs of pores ; these areas are directed 

 much backwards, which makes the width of the lateral interam- 

 bulacra proportionally greater. The apical disc is nearly central, 

 but nearer the anterior border ; it has four large genital pores, 

 and five well-marked eye-holes. The single ambulacrum is almost 

 identical in length and width with the posterior pair ; the apices 

 of all the ambulacra are rather rounded than lanceolate. The 

 lateral interambulacra we have said are very wide, but the single 

 interambulacrum is narrow, and forms a conspicuous prolon- 

 gation or beak-like process, which arches over the upper border 

 of the round anal opening, situated rather below the middle of 

 the posterior border, in an oblique truncature of the test : thi& 

 beak-like process is not seen in the small specimens before us ; 

 it would therefore appear to be a character of the adult con- 

 dition only. The base is slightly concave towards the mouth, 

 which is situated nearer the anterior border ; it has a pentagonal 

 form, with five small oral lobes covered with tubercles ; between 

 them, the terminations of the ambulacra form five short pori- 



