HALIOTIS. 23 



ing to Mr. Hanley, has occasioned some doubt, but the 

 characters are not sufficiently decided for separation. In this 

 species the young shells are generally ratlier narrower than 

 when more mature. Fig. 115 represents a very ordinary 

 appearance of the younger stage, and it seems probable that 

 the H. striata of Linneeus is from a similar young specimen, 

 of which there are several in his collection. 



21. BiSTRiATA, f. 99, 100, Grtiel. — Testa B. tuberculatcB 

 similis, sed liris validis rugosis elevatis, decussatis, plerum- 

 que alternatis sculpta. — Like T. tuberculata, but having 

 thick raised ribs roughened with cross striae, unequal and 

 sometimes alternate. It is difficult to find a definite line of 

 demarcation between this species and the more coarsely 

 sculptured varieties of the preceding. 



22. ALTEENATA, f. 51, Sowevhy. — Testa ovata, concava 

 subviridis, maculis subquadratis super costas picta, costis 

 undulatis latis, altemis minoribus sculpta ; spira elevatius- 

 cula, lata, apertura argentea labio interno lato complanato. 

 — Distinguished by broad flattened, alternating ridges upon 

 which are painted occasional brown spots. The specimen 

 here figured is slightly undulated, but some occur in the 

 British Museum in which the undulations are raised into 

 thick wrinkles. 



23. AQUATiLis, f. 97, Reeve. — Testa H. tubeixulatcc similis, 

 striis spiralibus fere evanidis ; pallide fulva, maculis magnis 

 fusco-viridis angulatim undatis picta, versus marginem liris 

 sublaminatis concentricis rugata. — A shell in which the striae 

 are nearly obsolete, ranging between H. tuberculata and H. 

 laminata, having the form of one and a few laminated ridges 

 like those of the other. It may perhaps be only a variety of 

 the former, which sometimes shews similar ridges. 



24. SEPicuLATA, f. 60, Reeve. — Testa ovata subconvexa, 

 radiatim irregulariter plicata, spiraliter costellis erectis acute 

 rugosis lirata, fusco subviride variegata. Formed like //. 

 tuberculata, but ridged with close-set elevated and sharply 

 roughened riblets, which are much more close and equal than 

 those of H. bistriata. 



25. PERTUSA, f. 58, Reeve. — Testa ovata oblonga sub- 

 laevigata, spiraliter punctatim incisa, fusca, versus marginem 

 externum laminatim plicata ; foraminibus subconspicuis. — 



