There's a high dome on the top that protects the primary nerve cluster. it's meant to taper down to the "diamond shape" at the bottom; the secondary nerve cluster. When I read "nerve cluster" I think "soft" and "delicate."
Marco's drawing is illuminating as it is so far from ANYTHING that crossed my mind for this character's look.
I didn't take the Cardassia symbol as a literal or exact description but rather something the Cethenthe's form put Dakal in mind of. Ditto the "lamp" description. The whole crystalline thing is news to me. it's possible I missed or forgot that but I don't recall its body as being described that specifically.
I put the legs at the bottom because they just "felt" like that's where they should go.
I tend to shy away from hard straight lines because nature tends not to make organisms with hard straight lines.
Regardless of what's written in the books, every character I draw will have some version of the fleet uni on. The idea here is to create designs for a fictional animated series so, under those specs, simplicity of design and a certain uniformity of style from character to character have to remain in play.
The small, single figure illos take about 15 or 20 minutes to complete so there will be divergences or "mistakes" because they are all sort of fast and dirty impressions.
It took me longer to decide how tall the good doctor should be than to draw the illustration.