258 Mr. W. Clark on some undescribed Animals 



exserted. The animal is active and freely shows its points. 

 Common in the coralline zone^ but rather rare alive. 



This is the true Turho reticulatus of Montagu ; it is, however, 

 subject to considerable variation of the contour and quality of 

 the cancellations, which have led to the fabrication of some spu- 

 rious articles. 



This species has not before been described. The specific ap- 

 pellation of 'reticulata' must be substituted for ' Beanii;' — a 

 complimentary term ought not to take the place of the long- 

 accredited and not doubtful one of the admirable Montagu. 



Rissoa punctura, Montagu. 



This species has been confounded with the preceding, but 

 having met with many live specimens, it will be seen that Mon- 

 tagu has properly distinguished it. The animal is lively and 

 freely shows its organs, and in this instance I have it in my 

 power to effect a concentrated description ; it is in every respect 

 identical with the jR. reticulata, with the exception of a parti- 

 cular-seated and constant variation of colour ; the operculigerous 

 lobe is a very pale muddy reddish brown, but it is marked, on 

 each side close to the junction of the foot with the body, with an 

 irregular rather large dark smoke-coloured stripe, which is inva- 

 riably wanting in i^. reticulata. 



Though differences of colour are not generally to be received 

 as good specific characters, yet, when we see certain markings in 

 an animal in a particular position, which are always absent in one 

 that resembles it in almost every other point, we ai-e entitled to 

 consider them as fair specific differences ; and in this case di- 

 stinctness is corroborated by a considerable variation in the con- 

 tour of the two shells, the R. punctura being much smaller, with 

 more rounded and less tumid volutions, as well as having the 

 sutures more deeply impressed than in the R. reticulata. 



Since these observations I have taken many of this and the 

 preceding species, and in the present animal have always found 

 the dark lead-coloured marks on the operculigerous lobe, with 

 the addition under the neck, near the eyes, of a small red dot ; 

 but these particulars are absent in the R. reticulata, the same 

 parts being pure white. Both inhabit the coralline zone, and at 

 Exmouth the R. reticulata is strictly confined to a coralline area, 

 whilst the R. punctura occupies the interstitial grounds of that 

 district, in muddy patches, mixed with comminuted shelly spoil. 

 I cannot doubt the distinctness of the two. 



Rissoa soluta, Brit. Moll. 



The animal occupies a simply elegant minutely spirally stri- 

 ated almost microscopic pale yellow shell of 3-4 rounded volu- 



