28 McMURRICH 



As the definition I have given above suggests, such a distinc- 

 tion may possibly be found in the enclosure of the longitudinal 

 musculature of the tentacles and the radial musculature of the 

 disk in the mesogtea, an arrangement which seems to be ab- 

 sent in typical Cribrinas. It must be remembered, however, 

 that as in the case of C. clegantissinius described above, transi- 

 tional conditions between what is found in Urticina and in typ- 

 ical Cribrinas occur, and the absolute value of such a char- 

 acteristic is accordingly open to question. Personally I am 

 somewhat inclined to regard the distinctness of Urticina from 

 Cribrina as not proven, but prefer to await the discovery either 

 of additional species clearly belonging to the former genus 

 or of transitional forms which will clearly bridge over such 

 differences as may appear to exist between the two. 



4. Urticina crassiconiis (Miiller) Ehr. 



[For the synonymy of this species vide Andres ('83) and 

 Carlgren ('93).] 



Several specimens of this form, which has previously been 

 described for the West Coast by Verrill ('69), occur in the col- 

 lection and show considerable variation in their external char- 

 acters. 



Habitat. — The majority of the specimens were found attached 

 to stones under wharv^es and accordingly in shallow water. 

 Two, however, were found imbedded in sand to a depth of six 

 inches or a foot, being attached below to stones. This habit 

 does not seem to be a usual one for the species but Dic- 

 quemare ('73) has described it for individuals obtained by him 

 at Havre, and Teale ('37) speaks of individuals being partly 

 buried in sand on the coast of Yorkshire. 



External Form. — It does not seem necessary to give a de- 

 tailed description of this well-known form, but mention should 

 be made of certain peculiarities presented by the various speci- 

 mens. And first as regards the verrucae. These in all the 

 specimens were distinctly in vertical series, but their distribution 

 varied somewhat. In some specimens they were large and 



