118 ECHINODEEMATA. 



3. OPHITJRA PUNCTATA. Plate XXIX. 



I feel some hesitation in the application of the name of this species, 

 which is the largest of the Ophiurae belonging to the Scotish seas. 



The finest specimens expand eight inches, or somewhat more, be- 

 tween the tips of the opposite rays : Plate XXIX. fig. 1. 



The disc exceeds an inch in diameter, with a waving circumference, 

 the whole surface resembling a cushion entirely covered by microscopic 

 granules. The rays long, and taper, are invested by transverse elliptical 

 scales, with produced extremities, denoting so many segments. Each 

 segment is bordered by a cluster or set of smooth obtuse spines, with a 

 dark centre. The cartilaginous organ is covered with prominences. 



When the under surface is viewed, the form of the disc and di- 

 vergence of the rays are well exposed. 



PLATE XXIX. 



FIG. 1. Ophiura punctata? 



2. Section of a ray, enlarged. 



3. Disc, under surface. 



4. Spinous and cartilaginous organ, enlarged, a, b. 



5. Portion of the surface of another specimen, enlarged. 



Miscellaneous Observations. The preceding examples will afford a 

 competent general idea of the nature of the Asterias and Ophiura, in as 

 far as relates to the more prominent features of their structure and his- 

 tory. Content with this at present, I shall abstain from entering on 

 minutiae, in the expectation of some future opportunity of illustrating 

 the subject in detail. 



Several facts, especially regarding the Ophiura, require much eluci- 

 dation. The number of these animals is excessive, both of species and 

 varieties ; but fallacies have certainly exaggerated them. 



The form of many seems transient, and assuredly undergoes various 

 modifications, in advancing to perfection. Their precise changes are yet 

 problematical ; but while remaining so, the observer is exposed to the 

 hazard of introducing duplicates, or spurious species, into the genus. 



